Eye Witness Testimony (EWT) -
'The evidence given in court or police investigations by someone who has witnessed a crime or an accident.'
The DEVLIN REPORT stated that there were 850 criminal court cases where the only evidence of guilt was EWT in 1973. 74% of these led to a conviction. Therefore the accuracy of an EWT is essential...
Why might EWT not be as reliable as we assume?
Bartletts theory of reconstructive memory...
Bartlett said that memory is an active process. How we remember info is affected by our pre-existing knowledge, attitudes and expectations. Specifically if we have gaps in our memory, information from our schema* is used to fill in these gaps. (basically guesses what should be there)
*SCHEMA - organised package of information containing your knowledge about the world; it helps us to make sence of it all.
Factors that affect EWT...
ANXIETY - an unpleasent emotional state when you fear something bad is about to happen. You normally experience phisiological arousal.
Yuille and Cutshall. Surveyed 110 people who had witnessed bwteween them 22 bank robberies, who had actually been threatened by the robbers. (so probably felt high levels of anxiety) They showed a more detailed and accurate recall than onlookers. ---> this suggests that high anxiety leads to more accurate EWT. positive correlation
Loftus and Burns. Participants shown a crime on video. Some saw a less violent version and some saw an extremely violent version where a boy was shot in the face. These participants (saw more violent) were much less accurate in recalling the events leading up to the incident. ---> Suggesting the more violent, the more anxiety leading to a low accuracy of EWT. negative correlation
Yerkes-Dodson suggested maybe that the actual relationship between EWT and anxiety was an 'inverted u' shape when shown on a graph...
...meaning that low levels of anxiety mean that we are more inaccurate; a small to medium amount increases our arousal, improving the accuracy of memory. But that high levels have a negative effect on the accuracy of EWT. This may be because a certain amount of anxiety heightens our arousal and makes us take notice,but too much may mean that we are unable to concentrate and encode details.
Weapon effect (ANXIETY)
Loftus. In the first conditionn articipants heard about machinery failure, and then a man with greasy hands comes out of the lab holding a pen. In the next condition there was a hostile argument and then a man came out holding a knife covered in blood. Participants were given 50 photos to identify the man who had come out of the lab. The participants who witnessed the peaceful scene were more accurate in recognising the man than the people who had witnessed the more violent scence.
This may link to EWT because the weapon leads to higher anxiety which leads to an inaccurate EWT. (focusing on the weapon)
Factors that effect EWT... AGE of the witness.
Problems with children and EWT:
1. They want to get things right. In ID parades, children are more likely to point someone out even if its wrong.
2. They are easily affected by post-event information. (children ages 3-8 in a science demonstration. Parents read them a story which contained elements of the demonstration and novel information. When asked about the science demonstration younger and older children used the novel information in their answers. Showing that children are suggestable and easily influenced. Therefore adults have to be careful when asking.
3. The accuracy of their recall fades over time. - Flin et al questioned adults and children about an incident and then again 5months later. They found that children got worse, but adults stayed the same.
age. elderly people
ELDERYLY PEOPLE -age may effect accuracy of EWT.
1. Yarmey. Participants watched a stage event involving a knife. 80% of elderly people failed to mention the knife compared to just 20% of younger adults.
2. In the same way that children are susceptable to post event information, the elderly can also be mislead.
NOTE: we do not know why exactly afe if the witness effects accuracy. there are lost of factors that may influence people of different ages.
factors affecting EWT...
The effect of misleading information on the accuracy of EWT:
Another way to be given misleading info after you have witnessed an event is through leading questions. Studies of reconstructive memory have shown that even the wording of the question asked can affect peoples recall of an event.
Leading question - a perticular question phrased in such a way as to promote a particular answer.
For example: What colour was that man's hat. (suggesting that he was wearing at hat)
misleading info... Loftus and Zanni showed that leading questions could affect recall. 7% of participants asked 'did you see a broken headlight' responded 'yes'. Compared to 17% of participants when asked 'did you see the broken headlight'. Infact there was no broken headlight. --> These findings suggest that leading questions could prompt a particular answer which will lead to an inaccurate EWT.
Loftus' studies have been criticised:
:( Hawthorne effect. Where participants know they are being watched and therefore try hard to pay attention.
:( Demand characteristics.
:( Socially desirable bias - socially acceptable answers given.. not truthful.
:( Experimentor bias - experimentor effects the way the participants behave.
key study into leading questions. LOFTUS AND PALMER.
Aim- to find out wheather memory could be influenced by the type of questions people were aksed.
Procedure - 1) 45 students, shown series of car crash videos. filled in questionnaire. Students were split in to 5 groups. The critical question was on 'how fast were the cars travelling when they ____ into each other'. The 5 groups each had a different verb in the sentence. Smashed, collided, bumped, hit or contacted. 2) 150 students. presented with a questionnaire, using the verb hit or smashed in the critical question. 3) A third group was not asked about the speed ay all. (control group) A week later participants were asked 'Did you see any broken glass?'
Findings - avergae of estimated speed in exp 1: Smashed = 40mph, Collided = 39mph, Bumped = 38mph, Hit = 34mph, Contacted =31mph. Exp 2 Smashed (32%) was higher than hit (14%) Control group = 12%
Conclusions - The info presented after an event can significantly influence our perception of that event.
Criticisms - :( Lacks ecological validity (only watching a video) :( only used uni students so lacks population validity. :( Socially desirable answers given? :( Demand characteristics?
COGNITIVE INTERVIEW. (fisher and ceiselman)
Used to encourage the eye withness to recreate the original context in order to increase accessability of store information. There are 4 main strategies:
RECALL EVERYTHING: ask for every detail, even if you think its unecessary.
CONTEXT REINSTATEMENT: Mentally recreating the original environment. - If you place yourself back there you are more likely to trigger what you remember.
CHANGE PERSPECTIVE: What would others have seen?
CHANGING THE ORDER: Reverse. Trying to get as much info as possible. Although this may confuse people.
WHY does the COGNITIVE INTERVIEW work? ...
Endoding specificity: When we encode info the context in which it happened is also stored. Consistancy between the actual event and the recreated situation increases the likelihood of accurate recall.
Varied retrieval: Uses different retrieval roots.
Strengths and Weaknesses of the COGNITIVE INTERVIEW.
:) Meta analysis done by kohnken. 53 studies. Using the CI= 34% increase in amount remembered.
:) Real life - Stein and memon. Brasil. CI more effective than torture. Increased recall when using CI. Found forensically rich info.
:( These studies ^ lack ecological validity as done in a lab.
:( Criticisms of CI technique: Time consuming, some strategies more effective than others, CI is not effective for younger children as it is suggesting and repeating questions, so they get confused.