Grâce à la liberté dans les communications, des groupes d’hommes de même nature pourront se réunir et fonder des communautés. Les nations seront dépassées.
Friedrich Nietzsche (Fragments posthumes XIII-883)

Forensic Psychology - Open University (3)

1.3 Introduction to the investigation

You’ve seen how real investigations can lead to wrongful convictions and how careful the police have to be when working with witnesses. To help you understand the psychology behind eyewitness evidence, you will get the chance to try to solve a case using nothing but eyewitness testimony.
An armed robbery was (very realistically) staged in front of a group of witnesses and then investigated by the Greater Manchester Police. At the end of the course, it will be your job to try to work out how the crime took place and who the guilty suspects might be. You will then get a chance to watch the crime and see how well the police did in solving it. Will your own investigative powers be a match for those of the police?
At various points you will get to see the witnesses presenting different types of evidence, including audio recordings of their interviews. Your job is to try to work out which pieces of information give an accurate insight into the crime, and which might contain flaws or just be completely wrong.
One of the most important tools police officers use in an investigation is the trusty notebook. As you work through the course, you should keep track of the evidence in a notebook, and also note down any insights you have. This will be an invaluable tool when it comes to trying to solve the crime at the end of the course.
Out of consideration for learners working through the course slower than weekly, we ask that you do not return to earlier weeks and post spoilers in any of the forum threads.

1.3.1 Profiles of the police officers

You will follow two investigations, conducted by two different police officers. Both officers are entirely fictional. They are also quite extreme caricatures designed to highlight two very different approaches to police investigations.

Detective Inspector Jake Bullet

One investigation will be conducted by Detective Inspector (DI) Jake Bullet. Jake has been a police officer for a long time and is proud of his reputation for securing convictions even in cases with little or no evidence to go on. He values the experience he has gained and is wary of attending training courses and learning new techniques. More than anything he trusts his hunches and believes in following his nose. He approaches most investigations by using his considerable experience and knowledge of the criminal community to form an initial insight into who the criminal might be. He then investigates his prime suspect and has become very adept at building a watertight case that proves the suspect is guilty beyond a reasonable doubt.

Detective Sergeant Lara Sund

The other investigation is conducted by Detective Sergeant (DS) Lara Sund. Lara has participated in a number of serious cases, but has not served as long as Jake. She values her training as a detective and is always keen to attend new training events and learn new investigative techniques. Lara is wary of jumping to conclusions and always tries to avoid making any assumptions about the evidence she gathers. This sometimes means her investigations take longer than her more experienced colleagues, and involve collecting more evidence. She is a highly trained interviewer, who prides herself on using the latest techniques. She approaches her investigations by collecting as much evidence as she can, reviewing it and then forming hypotheses about what took place, which she then tries to disprove.
DI Bullet and DS Sund are not working together – instead you will be following two entirely separate and unconnected investigations of the same crime.
You will find that although Jake and Lara are investigating the same crime and talking to the same witnesses, the evidence they gather can sometimes be very different. You may draw on both investigations to help you evaluate the evidence that is gathered, and you will also be provided with help from relevant psychological research and theory. Ultimately, it is up to you to judge the facts and solve the case – will you trust your own hunches, or try and apply psychological knowledge?
Which detective do you think is most likely to solve the crime? Do you think modern police training techniques will help DS Lara Sund collect accurate and reliable evidence, or will the experience and knowledge that DI Jake Bullet has built up from a career spent working the streets prove to be superior?
Vote for the person you think will prove to be the best detective in the Effective detective poll.

1.3.2 Profiles of the witnesses

The investigation focuses on two witnesses.


Lila is a 54-year-old woman who is 5 feet 2 inches tall and weighs just under 8 stone. She is a very confident person, who describes her memory as being very good. She happily admits that her memory for trivia is not great, but is proud of her ability to recall past events and details about her friends and family.


Seth is a 35-year-old man who is 5 feet 8 inches tall and weighs about 12 stone. He views himself as unconfident and is not comfortable being put on the spot. He doesn’t think of himself as having a particularly good memory, and therefore tends to bow to others when it comes to recalling past events.
When listening to the two officers question Lila and Seth, remember that the two investigations are not connected. You can think of the investigations as happening in parallel worlds, allowing you to see how the witnesses respond to different investigative policing styles, without their responses to one affecting their responses to the other.
Like the two officers, Lila and Seth are fictional. However, the responses that they give as part of the investigation are based on those that were given by actual witnesses to the staged crime. The interviews conducted by the Greater Manchester Police were recorded, and analysed to reveal the types of responses and errors typically made by witnesses. These responses and errors were then incorporated into reworded extracts that were used to form the accounts that are given here by Lila and Seth. This was done to ensure that the accounts were as authentic as possible.
Next week, you will get the chance to hear and evaluate the initial statements that our two detectives, DI Jake Bullet and DS Lara Sund, managed to obtain from the two witnesses at the crime scene. For the remainder of this week, we will look at the psychology involved in deciding whether to intervene in a crime.

1.3.3 Why did no one intervene?

Psychologists have been interested in bystander intervention for more or less 40 years now, and the interest was sparked by a real life event, the murder in 1964 of a young woman called Catherine Genovese, who was killed one night in New York as she returned from work. Now, murders in New York suburbs were not particularly rare in those days, but one thing that captured the public imagination and also attracted newspaper headlines was the fact that subsequent police investigation revealed that as many as 38 witnesses were present when she was killed, rather 38 of her neighbours noticed that an attack was taking place in the street, and yet none of them intervened in a way that would prevent her killing. Out of the 38 witnesses, only one of them screamed "Leave the girl alone!" from the window, while another one called the police, but did so after it was already too late and Catherine Genovese was dead.
And after this event two psychologists, Bibb Latane and John Darley, decided to investigate why people didn't intervene in that case and decided essentially to start, to embark on a research project on bystander intervention. And the starting premise was that in everyday life we often find ourselves in the position of a bystander; we might witness someone's car breaking down, we might witness a medical emergency, somebody fainting in the street... we might witness a petty crime or a fire, or any kind of emergency situation like that, and Latane and Darley argued that in some situations people do intervene and help, in others they don't. And what they wanted to find out is what determines whether someone will help or won't, in other words they wanted to look at what are the aspects of the particular situation that will either inhibit or facilitate bystander intervention.
And in order to investigate this issue, they conducted a series of very clever psychological experiments in the laboratory. The main feature of these experiments is that they took place in a very controlled environment, which enabled them to manipulate very small aspects of the situation, and then observe and measure how that affects peoples' likelihood to intervene. So what they did is they conducted, or rather they staged, a number of emergencies whether someone experiencing an epileptic fit, a fire or somebody falling off a ladder, and they looked at in what situations people will intervene and in which they won't.
Now one key study that I will describe in more detail is one that they called the 'Lady in distress' experiment. What they did, essentially, was they invited students from the university where they worked to come to a laboratory on the pretext that they would take part in a piece of market research. Once they arrived to the laboratory, they were met by a young woman who gave them a bogus questionnaire. All this was just a deception, a pretext of getting them into the laboratory. As they sat in the room and filled in this bogus questionnaire, the woman left the room and they could hear her working next door. And as they were filling in this questionnaire, they would hear the following situation.
They would hear the woman looking through a drawer, climbing up a chair or a stepladder, and then they would hear her fall. The fall was followed by screams and cries for help. What Latane and Darley were interested in is basically how many of the participants who took part in the study individually would actually go and intervene in some way - call for help, go and offer their assistance etc. - and what they found is that in 70% of the cases out of the 30 people who took part in the experiment and repeated this procedure, 21 people intervened. Which suggested when people were alone in the room, or rather when people were the only bystander present, they're quite likely to intervene; in 70% of the cases they would intervene. In-line with the social norm that people should offer somebody help when they are in distress.
But then they manipulated the experimental situation further, and what they did is then rather than having one person arrive to the laboratory and fill this bogus market research questionnaire, they had two people do it. Two naive participants would come along and do it, and they were met again by the same woman who was the confederate of the experimenters and who was part of the deception, and then they would repeat exactly the same procedure except this time there were two people in the room. And their prediction was that actually in this situation, it was even more likely that people would intervene, because if most people intervene, then the likelihood of two people who won't in the room at the same time should actually be smaller, so in this case they predicted that people would be more likely to intervene.
But what they found was that this was not the case. In fact, in this instance in only 40% of the cases did one of the participants actually go and help the woman. In other words, what they showed is that just the presence of one other person in the room reduces the likelihood of someone intervening from 70% to just 40%. In the final condition that they did, they actually - rather than putting two naive participants in the room, they actually put one participant and one stooge, another confederate of the experimenters who was pretending to be a participant (he too was filling out the bogus questionnaire) but was instructed in advance not to do anything, in other words to ignore the emergency. In this situation, only 10% of participants actually went and helped the woman. In other words, being in the presence of a passive bystander, someone who doesn't intervene, reduces the likelihood of intervention from 70% to just 10%. This finding that just the presence of another person reduces the likelihood of intervention has become known as the 'bystander effect'.

Neither Lila or Seth attempt to intervene in the crime, which is hardly surprising given it was an armed robbery!
However, as well as the armed robbery we also staged a crime in a pub, featuring an unarmed fight between two men, which was seen by at least a dozen people. The scene was filmed, and many people who watched the film expressed surprise that not only did none of the witnesses attempt to intervene, not one called for help or even used their phone to call the police.
Not wanting to become involved in a crime or other serious situation is referred to by psychologists as ‘bystander apathy’, and is a phenomenon that has been well researched. In the film above you see Dr Jovan Byford (a psychologist from The Open University) talk about some of this research and about a famous case in which Catherine ‘Kitty’ Genovese was attacked and murdered in a street in Queens, New York. Although the facts were later disputed, the report of the murder at the time claimed that 38 of her neighbours witnessed the attack, but did not intervene.

1.3.4 Why just stand by?

One of the shortcomings of the particular research that Latane and Darley did is that the underlying assumption, and this was kind of part of their starting premise, was that if you want to look at bystander intervention, it doesn't really matter whether you're dealing with a murder in New York in the 1960s or whether you're dealing with students sitting in a room seeing white smoke coming out of a vent duct, in other words they argue that this is a case of a general category of phenomena, such as an emergency, and that people sometimes act and sometimes don't in an emergency.
In real life, we do know that the likelihood of intervention depends very much on the nature of the emergency and where it takes place, and what attribution we place on the causes of that emergency. People are less likely to intervene if somebody who is experiencing an emergency looks a bit scruffy like a drunk, or a drug addict, because they make a certain attribution that almost that particular emergency is self-induced. In other conditions, people as soon as they witness an emergency, will of course make some kind of attributions about what caused that emergency and on basis of that will make a decision whether to intervene or not. And of course I think the key thing to bear in mind is that in emergencies where somebody's own life is threatened are probably the ones where people are least likely to intervene, which is exactly why the cases when they do attract so much attention and people are hailed as heroes. The whole concept of 'bystander' is not simply a description of somebody's position in a situation, it is also a moral category. To say that somebody's a bystander is in many instances an accusation - somebody who stood by as something drastic happened. On the other hand, to say, in other situations to say that someone is a bystander is an excuse for non-action. To say "I'm not the perpetrator, I was merely a bystander." and this is quite an important thing to bear in mind, which psychologists often fail to consider. And that is that we're not dealing, in everyday life when we talk about bystanders these are not neutral categories and mere descriptions, they're also a way of attributing blame, excusing somebody's behaviour or making a moral judgement about somebody's actions in a particular emergency situation.

Is bystander intervention a general phenomenon, or is the nature of the emergency and who is involved important?
Do you think you would have behaved differently? The bystander effect tends to be something that many people believe would not apply to them, yet the research suggests that when we are put in that position we are very unlikely to intervene. Of course, it can be difficult to generalise from research which focuses on only one event.
In this video, Dr Jovan Byford discusses whether all emergencies are the same, regardless of if they are a murder in New York or students dealing with a smoke filled room, or whether the nature of the emergency might be important. In addition, he looks at how our attributions about the emergency affect our behaviour and whether we intervene or not.

1.5 Summary of Week 1

So far you have seen the impact that wrongful convictions can have and that mistaken identification by an eyewitness appears to be the leading cause in such miscarriages of justice. You have also seen that simply changing the instruction given to an eyewitness can have a profound effect on the accuracy of the evidence they provide.
You have been introduced to our two detectives and our two witnesses, and next week you get the chance to begin your investigation as the witnesses provide an initial statement about what took place in the crime.


Dror, I. and Charlton, D. (2006) ‘Why experts make errors’, Journal of Forensic Identification, vol. 56 no. 4, pp. 600–616.
Nijboer, H. (1995) ‘Expert evidence’ in Bull, R. and Carson, D. (eds) (1995)Handbook of Psychology in Legal Contexts, Chichester, Wiley, pp.555–564.
Scheck, B., Neufeld, P. and Dwyer, J. (2000) Actual innocence: Five days to execution and other dispatches from the wrongly convicted , New York, Random House.
Spencer, J. and Flin, R. (1993) The Evidence of Children: The Law and the Psychology , London, Blackstone Press.
Wells, G. (1978) ‘Applied eyewitness research: system variables and estimator variables’, Journal of Personality and Social Psychology, vol. 36, pp. 1546–1557.

2. Initial statements - Introduction

Last week we had a look at how fallible our memories can be, and how the outcome of an identity parade, can be dependent upon the information the witness is fed. This week we are going to look at how witnesses provide different types of information. As you'll see, eyewitnesses often find remembering certain aspects of a crime, much harder than others. The duration, lighting and distance from the crime can all affect the memory of a witness, and you'll see that the type of person we are can also affect the accuracy of the information we provide.
We'll also discover the impact that talking to another witness can have on our memory of an event.
Then we'll hear our detectives take their initial statements. DS Sund and DI Bullet have quite different styles of investigation, which will not only lead to them to uncovering different information, but also forming quite different views about what happened, and how. There's also a chance to evaluate their evidence and start forming your own conclusions. See you next week.

Before you hear the initial evidence provided by our two eyewitnesses, we’re going to explore some psychological knowledge concerning how accurately eyewitnesses provide different types of information.
Last week you saw that the outcome of an identity parade can be dependent upon the specific wording of the question that is asked of the witness. Simply asking ‘Who is it?’ can imply that the perpetrator is definitely present in the parade and, therefore, that the witness should select someone. The question asked of a witness is an example of a system variable, as it is under the control of the police.
However, there are also estimator variables, not under the control of the police, that are important to be aware of when evaluating witness evidence. Even if you cannot control for how long the witness saw the perpetrator, for example, it is still important to know what affect this might have on the accuracy of their memory.
Knowledge concerning the impact that estimator variables have on eyewitness testimony will be important when you come to evaluate the evidence provided by our two eyewitnesses.

2.1 Remembering different aspects of a crime

As a witness to a crime, there are many factors that can work to our disadvantage. The experience of viewing a crime can be very brief – perhaps even a matter of a few seconds – and we may not even realise that a criminal event is taking place until it is over.

Effective observation

Reliable evidence depends upon the witness being able to observe effectively. For example, accurate face recognition is dependent upon seeing the perpetrator’s face for a sufficiently long period of time (e.g. Ellis et al., 1977). Furthermore, the crime may take place in poor lighting and at some distance away. Research demonstrates that beyond a certain distance, and depending on the light, identification may be problematic. Researchers tested participants’ ability to recognise a target’s face at seven distances and nine illumination levels. Immediately after seeing the target face, participants were asked to identify the face they had just seen from an array of photographs (Wagenaar and Van Der Schrier, 1996). As a result, the following guideline emerged regarding what observation conditions are needed for identification evidence to be sufficiently accurate (known as the ‘Rule of 15’):
  • the maximum distance is 15 meters from the event
  • the minimum illumination is 15 lux.
Lux is a measurement of luminance, where 0.3 lux is equivalent to night time with a full moon; 30 lux is equivalent to a badly lit room; and 300 lux is equivalent to a brightly lit room. It is important to note that this research does not mean that identification will be accurate if the perpetrator was seen from less than 15 metres and at more than 15 lux, just that identification evidence cannot be relied on unless these requirements are met.
This study demonstrates that although estimator variables are not under the control of the police/criminal justice system, research can still investigate their influence and provide useful advice – in this instance, by providing information relating to the feasibility of an accurate identification.
What about other judgements that witnesses might be asked to make?

Estimates of time and distance

Research suggests that, generally, we are not very accurate in our estimates of how long something lasts (temporal duration) or of distance. We may overestimate the length of events of short duration, sometimes by as much as 500%. Many studies (e.g. Block, 1978) have shown that a time interval containing unfamiliar, less predictable, complex or many components (as when solving a complex puzzle) is estimated to be significantly longer than an interval of the same duration that contains more familiar, more predictable, simpler or fewer components (as when doing simple arithmetic).

Estimate of date

Our ability to provide the correct date for an event may also be poor. Research testing participants’ ability to date episodes they had personally experienced showed that accuracy in dating was dependent on how long ago the episode occurred (known as the retention interval), and that accuracy decreased rapidly as the retention interval lengthened. When asked about experiences that had taken place in the previous week, participants tended to date accurately 85–90% of the time. For experiences that occurred over three months ago, however, accurate dating dropped to 15–20% (Thompson et al., 1996).
Furthermore, many studies have reported a phenomenon known as ‘forward telescoping’, a tendency to assign a date to an event that is more recent than the actual date of occurrence. This tendency has been observed as soon as eight weeks after the event occurred. Telescoping is thought to arise because we overestimate the frequency of events occurring during a certain time period, and therefore mistakenly import or bring forward events that actually happened earlier.

Estimating height and weight

Our estimates of people’s height and weight are also frequently inaccurate. Researchers asked 588 participants to estimate the height and weight of 1 of 14 males who had previously asked them for directions in a busy city centre (Flin and Shepherd, 1986). They found errors for height judgements to range from an underestimation of 14 inches (35.56 centimetres) to an overestimation of 8 inches (20.32 centimeters). Judgements of weight ranged from an underestimation of 98 lbs (44.45 kilograms) to an overestimation of 36 lb (16.33 kilograms). The results showed that the height of all 14 males was underestimated by 6 inches (15.24 centimetres) by at least one participant.
Generally, these findings indicated a ‘trend of underestimating above-average characteristics and overestimating below-average characteristics … indicating a general regression to the population mean’ (Flin and Shepherd, 1986, p. 35). Their results also indicated that the participant’s own height and weight was used as a norm or anchor against which the height or weight of the male was estimated (although this effect was small in female participants’ judgements about height, and absent in their judgements about weight). Therefore, when asking witnesses to estimate such characteristics, it may be helpful to obtain relative judgements. For example, if a perpetrator is seen standing in a doorway, their height may be judged by asking how much shorter than the door the perpetrator was.

2.1.1 The influence of witness characteristics

It is also important to consider estimator variables to do with who the witnesses were, as well as variables to do with the conditions in which the crime was witnessed. In particular, personality, sex and age have been explored in relation to witness characteristics.
Kapardis (1997) reviewed the evidence regarding the influence of a range of personality characteristics. Much of this evidence tended to consider performance on face identification tasks and the findings are rather tentative. In many cases, the personality characteristic is thought to influence arousal (a psychological and physiological state, in which various parts of the brain show increased activation leading to the person being alert and ready to respond to stimuli) and, as you shall see, it is not always clear how this impacts on witness testimony. For example, neuroticism (a concept from personality theory, characterised by such traits as anxiety and emotional instability) may interact with arousal level to influence memory. The identification accuracy of those low in neuroticism has been found to increase as arousal increases from low to moderate, but the reverse was observed for those high in neuroticism.
Might experience matter? Would a police officer provide more complete and accurate testimony, should they witness a crime? The weight of the evidence suggests that their testimony is no more reliable than that of members of the public. However, a trained police officer may find witnessing a crime less stressful than other people.


With regards to sex, some studies have shown that female participants provide more reliable ‘testimony’ than males, whereas others have found the reverse, or no difference. Such inconsistent findings suggest that differences between males and females vary or disappear depending on the factors surrounding the event that the witnesses are observing and reporting. For example, males have been found to be better than females at remembering details of a violent incident in several different studies, but no difference has been observed between males and females when shown a non-violent incident (e.g. Clifford and Scott, 1978). Then again, differences can emerge according to the type of details being reported. Some studies have found that females are more often able to remember or reconstruct the precise date of an event, but exhibit the tendency to overestimate the temporal duration of an event more than males. Therefore, while the sex of the witness may impact upon the evidence provided, its influence is by no means clear-cut and it is not a particularly useful variable to consider when evaluating eyewitness evidence.


It is known that our vision and hearing may deteriorate notably from around 70 years of age, and there may also be a decline in attention with ageing. All of these (especially quality of vision) will impact upon the completeness and accuracy of eyewitness accounts. However, the majority of research on the role of age in reliable witnessing has concentrated on children. Generally, young children have been found to provide less information than adults, and are less accurate than adults with details of time, temporal order, estimates of distance and speed, and estimates of height and weight. These findings are consistent with research that suggests an improvement in a variety of cognitive skills with age. However, children as young as six years may perform at adult level in their reporting of an event, and this is dependent on a range of factors, including what they are questioned about and how they are questioned. In other words, and assuming appropriate questioning techniques are employed, younger children may on average remember less accurately than adults, but some individual children will remember as accurately. However, the majority of research on the role of age in reliable witnessing has concentrated on children (e.g. Ceci and Bruck, 1993).

2.1.2 Co-witnessing

It is important to consider whether there was more than one witness to a crime, and how each witness’ memory and testimony might be affected by talking to other witnesses.
Helen Paterson is a Senior Lecturer in Forensic Psychology at the University of Sydney, Australia, and a world expert on co-witnessing, a term that refers to crimes that are witnessed by two or more people who then share accounts of what happened. In this co-witnessing interview, Helen describes the impact that co-witnessing can have and how this topic has been researched.

What sparked your interest in the effects of witnesses discussing events?
Witnesses tend to discuss the event with one another. This happens very reliably and consistently. And just to give you an example there is one story I heard about a man who was actually writing his thesis, this was many years ago, and I like this story because I was writing my thesis at the time I found out about him. What happened was he was actually wanting to write the final version of this thesis, and this was back in the day when people used typewriters. So he went up to the shops to purchase some new ink for the typewriter. He came back home and started to work on his thesis. A little while later there is a knock on the door and it's the police. And the police have come to arrest him and charge him with bank robbery. Apparently while he was at the shops he had robbed the bank. Well, it turns out that he was actually found innocent and one reason that he suggests that he was wrongfully charged with this crime was because one person had mistakenly identified him and then spoken to others and other people began to believe that he was the one who committed this crime. What's quite interesting to know for many of the people perhaps listening is that this man is actually very well known in the UK. His name is Peter Hain and he is a current member of parliament in the government and he was actually leader of the House of Commons under Tony Blair.
How did you go about investigating the impact of witnesses discussing what they had seen?
What we decided to do was we wanted to survey witnesses to find out how common this was and what we found in an initial survey that we gave out, the vast majority of witnesses report that there are actually other witnesses present when they view the event.
When we then went on to interview the people who had been around multiple witnesses when they - when they saw the event we found that the vast majority, that is 86 per cent, reported they talked to other witnesses about the event. We asked them what they talked about and the number one reason they talked about the event with one another was they're providing information. So they're actually talking about details of the event with one another.
I conducted a study and we wanted to compare to see how much information people - post event information people would incorporate into their memory accounts of an event if they encountered this information in one of several different ways. And whether they encountered the information through leading questions, which is commonly studied through reading about it in the media report or through co-witness information. And there were two different types of co-witness information we compared. Sometimes when witnesses discuss the event with one another we call this direct cowitness information. Or sometimes witnesses can encounter information indirectly, that is through a third party. For example if a police officer says oh the other witness mentioned that - that the suspect - that the culprit had blue eyes. Do you agree with this statement? So what we did was we had participants view an event and then we gave them post event information through one of these different methods either indirect, co-witness information, direct co-witness information, media report, leading questions or we had a control condition that didn't give any post event information. With this post even information we gave them some accurate information and we also gave them some items of inaccurate information.
What did your findings reveal?
What we found overall was that participants who encountered this information drew on either direct co-witness discussion or indirect and co-witness information. They were far more likely to include this information in their reports than those who encountered the information through leading questions and media reports. So this is actually suggesting to us that co-witness information is extremely influential and whether it be accurate information or inaccurate information they're far more likely to incorporate this information into their account of what happened during the events.
What we find is that co-witnesses reliably and consistently report information that they receive from a co-witness after an event. This is an extremely strong effect and it's been replicated in many studies. Essentially if you take Asch's conformity paradigm and the misinformation effect paradigm bring them together, you get a very strong effect. In fact I've never conducted a study where I haven't found the co-witnesses are very influential for memories.
Given your findings, is there anything that can be done to reduce co-witness effects?
In fact the effect is so powerful that you know we just can't get rid of the darned effect and that's been our problem more than anything else. We've tried a variety of different methods to try to see if we can get witnesses to discount the information that they've been given from a co-witness and only report their own memories for the event. And we find this actually doesn't work. We can't eliminate it. We can't stop them from reporting the co-witness information because it seems to become part of their own memory for the actual event.
In general, legal authorities would prefer it if witnesses don't talk about the event with one another. For example the legal concept of hearsay embodies the notion that a witness's assertions should be based on their own experiences and not those of another and actually there are guidelines that exist in the United Kingdom which suggest that witnesses should be separated and instructed not to discuss the event with one another.
Remember that our crime was witnessed by two people, so when evaluating the evidence they provide you should take the effects of co-witnessing into account.

2.1.3 Impact of estimator variables

There are many variables that will influence the accuracy or completeness of the testimony of a witness. These variables are estimator variables and therefore not under the control of legal professionals. Knowing their potential influence does help us judge how much weight to place on the information provided by a witness, and also helps us to evaluate whether one witness might be more accurate than another.
Later, you will hear the initial statements provided by our two witnesses to both DI Bullet and DS Sund. When you listen to the evidence, see if you can apply the knowledge you have gained here in order to evaluate it.
Below is a list of some of the key factors that you might want to keep in mind:
  • Confidence does not necessarily mean accuracy. Despite her best efforts and being sure she was correct, Jennifer Thompson identified the wrong person.
  • Actions may be remembered better than details.
  • Variables such as how far the witness was from the crime, what the illumination was and how long the witness was exposed to the event and the perpetrators can all have an effect on the accuracy of witness testimony.
  • People are generally not good at judging either time or distance – we often overestimate the duration of short events, particularly if the event is complex.
  • We tend to be poor at dating events – forward telescoping means we often assign a date that is too recent.
  • Estimates of height and weight are not accurate – we have a tendency to underestimate above-average characteristics and overestimate below-average characteristics. The witness’ own height and weight might be used as an anchor against which the height or weight of others are estimated. This means it is a good idea to ask for relative judgements, e.g. how tall was the perpetrator in relation to the doorway?
  • The gender of the witness may impact upon the evidence provided, but its influence is by no means clear-cut.
  • Age can have an effect. Over the age of 70, hearing, vision and attention decline, and children will generally provide less information and be less accurate than adults.
You also heard about the potential problems of co-witnessing. This does not fit the estimator/system variable distinction very well, as it is partly, but not entirely, under the control of the police:
  • Co-witnessing – allowing witnesses to talk to one another, including interviewing them together, will lead to considerable convergence in their testimonies. Witnesses can form a memory of something happening from listening and talking to another witness. So, consistency in testimony is to be expected if the witnesses have had a chance to share memories. Such consistency should not be seen as confirming the facts reported.
In addition, remember that the way in which a question is asked can have a dramatic effect on the response of a witness. We’ll look at questioning later on, but for now remember that the question ‘Who is it?’ tends to make a witness select someone from an identity parade because the question implies the perpetrator is present, and therefore, that the witness should choose someone. When evaluating the witness statements, consider how the detectives ask their questions. Are they giving the witness the opportunity to respond based on their own memories, or are they suggesting the answer to the witness?
In the next sections, you’ll find out about the crime committed and hear the witness statements taken by the two detectives, DI Bullet and DS Sund. First take a look at the timeline of the crime and police response:

Timeline of the crime and police response

16:24, Wednesday afternoon – the police receive a number of emergency calls reporting a possible armed robbery in progress.
Three are from people working in office buildings adjacent to where the crime is taking place who report hearing gun fire; one is from a pedestrian passing by the end of the road who sees an armed, masked man run past; and one is from a car driver who narrowly avoids a collision with a speeding car.
16:26 – An initial response unit is dispatched to the location reported in the emergency calls.
16:32 – The police receive a call from a mobile phone from two eyewitnesses to the crime, who confirm an armed robbery has taken place and also that the robbers kidnapped a young woman, called Liz, a friend of the witnesses who was with them when the crime started.
16:36 – The initial response unit arrives at the crime scene. The two eyewitnesses who made the call are still there, but the robbers have clearly left. The street in which the crime took place is cordoned off.
16:48 – A detective from the Criminal Investigation Department (CID), Detective Inspector Jake Bullet, arrives at the crime scene and, after a brief conversation with the officers already there, talks to and obtains an initial statement from the two eyewitnesses.

2.2 DI Bullet takes witness statements

In the next activity you will listen to an audio recording of the initial statement taken by DI Bullet. As you listen to it, make a note of any evidence about the crime that you think might be useful in solving it. Remember, try to evaluate what you hear in terms of what you have learned about eyewitness memory.

OK, now, I understand the two of you witnessed an armed robbery and a kidnap. We need to catch the guys that did this fast and the only clues that we have to go on are what you can tell me. I'll talk to you later at the police station and we can take full statements, but for now I just want you to focus on the key details of what happened and particularly what the robbers looked like.
Now, I understand the suspects drove up and jumped out of a car, now, could either of you describe it?
Yes, it was a large silver car and the number plate was NG58 VXW. I knew it was going to be very important to remember the number plate and I've got a really good memory. I don't know much about cars and it was at least a hundred feet away, so I can't tell you the make, just the number plate. But it was silver and it looked very new and expensive. It had a red light in the back window and four doors. I know it had four doors because I remember them all being open at once. That must've been when the men jumped out and opened the ones in the front as well as the two back doors. I had a good view of the car; I kept staring at it as the robbery went on for a bit, easily 10 minutes, so I had a lot of time to study the plate.
I don't remember the car pulling up, just that the robbers were suddenly there, jumping out of the car I suppose. I remember the tires screeching though, so I guess the car must've pulled up fast. I was pretty shook up, so didn't think to look at the number plate, but yeah, large silver car sounds right. Tires must've screeched as they drove around the corner. Then they all jumped out and started waving guns about, it was terrifying. I don't have a good memory of the details, but yeah, they must've all jumped out of a large silver car and if I had to guess I would say it was an Audi, but I'm not really sure.
Great, thank you. Lila you're a real star for remembering that number plate. So, let's take it from when they all jump out of the car, what happened then.
There were 3 of them, 4 including the driver. The three jumped out and ran over to the security van and grabbed hold of two of the security guards. They all had guns and they forced the guards to the ground. Two of them were wearing balaclava masks so I couldn't see their faces. The third, who had a fight with one of the guards and hit him had a hood, I think, but it wasn't up so I could see his face. He had very curly, shoulder-length black hair, was about 5 foot 3 and had quite dark skin. I would say he's in his early 20's, say... 22? and maybe he was Spanish or Italian? Or probably Asian. Yeah I would say he was probably Indian. They didn't say anything so I didn't hear an accent and the other two kept their masks on, so I don't know what they looked like. But all three seemed pretty similar, you know, quite stocky? Not fat necessarily, but stocky, like they'd all worked out a lot, like they were bouncers maybe. They all had on dark jackets that had hoods and all of them were wearing army trousers, you know? Like, they have camouflage on them? Two of them, they aimed their guns at security guards whilst the third grabbed a case. The case was on a chain, so he had to break the chain with some sort of tool.
So you got a good look at the unmasked one that was fighting with the guard. Would you be able to identify him if you saw him again?
Yes. I got a good look at him and I would definitely be able to recognise him again.
Seth. Talk me through what happened.
OK, they all jumped out the car, firing shots into the air. Two ran to the van and made the guards get out. I don't really remember much, but I think Lila's right, the one who didn't have a mask was being really aggressive and fighting with one of the guards. He was about... 20? That's the Asian one isn't it? About 20 and... 5 foot 3 or 4?
Is there any more that you can tell me about these three - were they wearing camouflage, dark jackets?
I think that's right, yeah, camouflage. A bit like soldiers, only they had jackets on. They were all muscly. Really stocky, like they reminded me of bouncers or something. The Indian guy started fighting with one guard, and he hit him in the head I think? He fought the guard to the ground and he stole the case that was chained to his wrist. The others had masks so I didn't really see them. Oh, and now I think about it, there was something a bit odd about one of them. I remember thinking that one of them was different, almost... almost childlike maybe? Or a like a woman maybe? But you know, I didn't really get a good look at them so it's probably nothing. They didn't really come over to us and I didn't want them to. All of them were similar - dark jackets, camouflage trousers... I'm sorry, I'm not sure I can say any more than that.
Well that's great guys, you're doing really well. We've got the number plate and a good description. Now, let's deal with the kidnap.
That was the worst bit. I was hoping they were just gonna ignore us, but then the driver got out the car and he just started running towards us. He had a gun, like, a shotgun, and he was firing it in the air and shouting. I was really scared. He was a tall white guy, hard looking, short hair. He just ran towards us and grabbed Liz. She was just standing there with us but he grabbed her and he dragged her screaming back to the car and... well, then they were gone, with Liz.
Was it the driver? I mean, someone definitely grabbed Liz... no you're right, it must've been the driver, as the other three were fighting with the security guards. The driver was firing his shotgun in the air and shouting at Liz. He was white, and older than the others, probably... 30? and a lot stockier, you know, but also a lot taller. I mean well over 6 foot, probably... 6 foot 3 or 4? He was a really tall guy, he towered right over Liz, but really well built, too. He was dressed like a soldier, camouflage all over and no mask. He had very short hair.
How short? You mean like a soldier would have, a crew cut?
Yeah, like a soldier, like a soldier's crew cut, and he also had a soldier's face, if you know what I mean, you know, like he was a very hard man used to giving orders. He dragged Liz back to the car, bundled her in and then drove off, really fast.
So you both got a good look at the driver who kidnapped Liz as he was very close to you. Would you be able to identify him if you saw him again?
He was very close to us, so yes, I would definitely be able to identify him.
I'm not sure. Now that I think about it, there was something odd about his face. Was he wearing sunglasses? That seems really odd but I think he was. They had really dark lenses and silver frames. I just don't remember his face. Maybe he had like a cap on and sunglasses so he was hard to see. I remember the shotgun, which he kept firing, but I'm sorry, I'm really just not sure what he looked like.
Right, I think we've got plenty to be going on with, let me just go over my notes with you. Lila, you said a large silver Audi, new and expensive looking, screeched around the corner, and and the number plate was definitely November-Golf-5-8, Victor-X-ray-Whiskey.
Yes, the number plate was definitely NG58 VXW.
Good. After that, four guys jump out, all wearing army fatigues and dark jackets and they start firing guns into the air. Three of them run over to the security fan, and the driver ran towards you, threatening you with a shotgun, grabs Liz, drags her back to the car. The other three fight with the guards, use a tool to cut the chain attaching the case to one of the guards and then steal it. Is that pretty much it?
That sounds right to me.
Now for the descriptions. The driver is a Caucasian male, in his 30's, 6 foot 3 or 4, dressed like a soldier and with dark hair in a crew cut. The guy who steals the case is an Asian male, in his 20's, 5 foot 3, stocky with long, dark, curly hair. All are armed with shotguns.
Yes, yep, you've got it all.
Yeah... I mean, I think that's right... it was just really scary to go through, but that summary makes sense, so... that's how it must've happened.
So, some very useful details there. Lila was a perfect witness - not too scared, remembered loads of details, really managed to keep her head and come through for us. Not so sure about Seth, he was obviously terrified. I don't trust his memory about the car being an Audi, but as Lila remembered the number plate I don't need to. She also gave us a good description of the suspects - 4 men, 2 with masks - the unmasked guy's Asian, probably of Indian ancestry, in his early 20s, has long, thick curly dark hair. He's 5 foot 3, very stocky. The driver was Caucasian, early 30s, 6 foot 4 and well-built. He had a crew cut and wore army fatigues. I think Lila is likely to be very reliable. I think all that business from Seth about sunglasses and not being able to see the driver's face is just because he was so scared. He probably didn't get a good look at the guy and that's why he can't remember his face.
The initial statements from Lila and Seth revealed a wealth of information about the events of the crime and also about the perpetrators. How did you get on noting down potential evidence?

2.2.1 Evaluating the statements

To help you, two lists of potential evidence have been provided below, one to do with what happened and one about what the perpetrators looked like. Have a look through the lists and try to decide how reliable each piece of information is. Be sure to note down those statements you think might be accurate.

What happened

  • Lila confirms that the suspects drove up and jumped out of a car. (Lila)
  • The car was new, expensive, large and silver. It had four doors and the number plate was NG58 VXW. (Lila)
  • The car stopped 100 feet away. (Lila)
  • The crime easily lasted for 10 minutes. (Lila)
  • Seth confirms that the perpetrators jumped out of a car. (Seth)
  • The perpetrators waved guns around as they jumped out. (Seth)
  • Seth confirms the car was large and silver. (Seth)
  • The car was an Audi. (Seth)
  • There were four perpetrators, one who was a driver. (Lila)
  • Three of the perpetrators forced two security guards to the ground. (Lila)
  • One perpetrator, who was not wearing a mask, fought with a guard and hit him. (Lila)
  • The two masked perpetrators aimed guns at the guards, while the unmasked perpetrator cut free a case chained to one of the guards. (Lila)
  • The two masked perpetrators fired shots in the air. (Seth)
  • The two masked perpetrators made the two guards get out of their van. (Seth)
  • The kidnapper was the driver. (Seth)
  • The driver had a shotgun which he was firing in the air while shouting at Liz. (Seth)
  • Lila confirms the kidnapper was the driver. (Lila)
  • The driver dragged Liz back to the car, bundled her in and drove off. (Lila)

What the perpetrators looked like

  • The unmasked perpetrator had very curly, shoulder-length black hair. (Lila)
  • The unmasked perpetrator was about 5 foot 3 inches. (Lila)
  • The unmasked perpetrator was 22. (Lila)
  • The unmasked perpetrator was probably of Indian ancestry. (Lila)
  • The masked perpetrators were stocky and looked like bouncers. (Lila)
  • The perpetrators were dressed in dark jackets and army trousers. (Lila)
  • Seth confirms the unmasked perpetrator is Asian, about 20 and 5 feet 3 or 4 inches. (Seth)
  • Seth confirms that the perpetrators looked stocky and like bouncers. (Seth)
  • There was something odd about one of the masked perpetrators – they looked almost child-like or like a woman. (Seth)
  • The driver was a tall white guy. (Seth)
  • The driver had short hair. (Seth)
  • The driver was probably in his 30s. (Lila)
  • The driver was about 6 foot 4 inches. (Lila)
  • The driver was dressed like a soldier. (Lila)
  • The driver had a crew-cut hairstyle. (Lila)
  • The driver was wearing sunglasses and a cap. (Seth)

2.2.2 Re-evaluating the statements

You know now that a question can suggest a response, that the co-witnessing effect tends to make evidence from two witnesses very similar, and that people tend to judge height and weight badly as the judgements are made relative to their own build.
To help you evaluate the statements taken by DI Bullet, in the next activity you look at potential ways that evidence can become biased. For each question, you will be provided with a specific statement that was obtained by DI Bullet in the audio you heard. Your job is to decide whether the statement is likely to have been biased by one of these three factors:
  • Biased as it was suggested by the question asked – for example, did DI Bullet ask a question in a way that suggested what the answer should be, or suggest information to the witness that they had not mentioned before?
  • Biased because of the co-witnessing effect – did the witness remember the information themselves, or had they heard another witness say something similar?
  • Biased as witnesses tend to over and underestimate height, weight, distance and time.
Alternatively, the evidence might not have been influenced by any of the above factors, in which case you should select:
  • Potentially unbiased.
The statements that appear in the quiz are all taken from the recording of DI Bullet you heard in DI Bullet: initial statements. Do feel free to re-listen to this audio as many times as you like.