Accuracy of Eyewitness testimony

Accuracy of Eyewitness testimony

1. plays a critical role in criminal investigations- inaccurate eyewitness memory is the main factor leading to false convictions in US

2. Loftus and Palmer (1974)

   • Procedure: 45 American students formed an opportunity sample- laboratory experiment with 5 conditions, only one of which was experienced by each participant (independent measures design). 7 films of traffic accidents ranging in duration from 5 to 30 seconds. Participants asked speed of cars prior to accident, different groups given different verbs e.g smashed, bumped, collided
   • Finding: the estimated speed was affected by the verb used- The participants in the 'smashed' condition reported the highest speed estimate(40.8), followed by 'collided'(39.3), 'bumped'(38.1), 'hit'(34.0) and 'contacted'(31.8) in descending order
   • Experiment 2: New set of participants divided into 3 groups & shown a film of a car accident lasting one minuted- group 1 given verb smashed, group 2 given verb hit and group 3 did not have a question. participants returned 1 week later + asked 'did you see any broken glass' (no glass in film)
     • Finding: Participants gave higher speed estimates in 'smashed' condition + more likely to think they saw broken glass = research suggests that memory is easily distorted by questioning technique and information acquired after the event can merge with original memory causing inaccurate recall or reconstructive memory.

3. Evolution

   • Laboratory experiments may not represent real life because people don't take the experiment seriously and/or they are not emotionally aroused in the way that would be in a real accident
   • Criticism: Yuille and Catchall (1986) interviews 13 people who had witnessed an armed robbery in Canada. interviews too place more than 4 months after the crime & concluded two misleading questions- despite this the witnesses provided accurate recall that matched their initial detailed report

4. Anxiety

   • Deffenbacher et al(2004) meta-analysis of 18 studies looking at effects of heightened anxiety on accuracy of eyewitness recall => considerable support for hypothesis that high levels of stress negatively impacted accuracy of ETW
   • Christians and Hubinette (1993) questioned 58 real witnesses to bank robberies- witnesses who were threatened in some way were more accurate in their recall + remembered more details than those who had been onlookers & less emotionally aroused
   • Weapon-focus effect: Johnson and Scott(1976) two conditions, one involving a weapon and one not. In condition 1 participants overheard discussion in adjoining room, a man emerged holding a pen+ grease on his hands - In condition 2 discussion was more heated and a man emerged holding a paperknife covered in blood
     • asked to identify man from 50 photos- participants in condition 1 49% accurate, compared with 33% accuracy in condition 2 = suggest weapon may have distracted attention

5. Age

   • Parker and Carranza (1989) compared primary school children & college students in ability to correctly identify a target individual after slide sequence of a mock crime. in photo identification task, child witnesses had a higher rate of choosing than adult witnesses BUT more likely to make errors of identification than college students
   • Evaluation
     • Criticism: Majority of studies have tested college ages student who are asked to correctly identify the faces of similar-aged targets= ignored the possibility that participants may simply have superior memory for faces in their own age group
   • Memon et al (2003) accuracy of young 16-33 and older 60-82 eyewitnesses. When the delay between 'incident' and identification was short 35 mins = no difference in the accuracy of the two age groups BUT when delayed by one week the older witnesses significantly less accurate

6. Evaluation

   • Loftus et al(1987) monitored eyewitnesses eye movements- found presence of a weapon causes attention to be physically drawn towards the weapon itself and away from things such as person's face