WEEK 5 - identifying the perpetrator

In us US, how many people a day become defendants after being identified from lineups?

200 people

in around ___% of exonerations, at least one eye witness made a false identification

75%

what is the least reliable form of evidence and is pursuasive to juries

eyewitness identification

what are estimator variables?

variables to do with a persons memory for the offender

what are system variables?

how the CJS elicits visual identification evidence

the way in which we elicit eyewitness identification evidence can make things difficult for witnesses

what are the 6 types of estimator variables, describe them/ give example

1. stable witness factors - age, ethnicity

2. maleable witness factors - alcohol consumption, tiredness

3. stable target factors - facial distinctions e,g tattoo

4. malleable target factors - disguises

5. enviornmental facotrs - light levels, visibility

6. post even factors - delay, exposure to misinformation

what are the key eyewitness descriptions in order of reported the most

hairstyle

eyes

nose

face shape

what is verbal overshadowing?

giving a description of the person actually makes you worse at identifying the person from the line up

what are systems variables made up of?

• verbal descriptions

• facial compositites

• mugshot books

• line ups

describe why we dont really use verbal descriptions?

often too brief to be forensicaly useful

focus on external features and other features that are easily changed

when witnesses have initially provided a highly detailed description, investigators often place more weight on subsequent visual identification

there is no reliable association between what?

the nature of the verbal description and subsequent visual identification accuracy

what are facial composities?

sketch artists, manual systems

need to consider the ease with which facial composities are constructed and the ease in which they are recognised

people are poor at constructing accurate facial composities even of family members

what is better than facial composities?

systems that allow for whole face proccesing

e.g evofit - shows you many pictures that are simialr to the person you picked - the will continue to show more based on what you pick

caricatures also show promise

what are mugshot books?

when witnesses are asked to look through albums containing mugshots of known offenders - can contaminate identification performance by not finding the source of our memories

who is an example of misidentification in a line up?

ronald cotton

describe the difference between a target present and target absent line up

target present - target is in the line up and has to identify the suspect, if they pick foil they are wrong because they are innocent

target absent - if suspect is innocent, everyone in the line up is innocent

what is instruction bias?

there is always a chance that the lineup doesnt contain the perp

despite this witnesses are reluctant to reject lineups

target absent lineups lead to an increase in false alarms

memon, hope and gabbert conducted a study looking at instruction bias, what did they do and find?

• participants given a post line up questionarie

• 90% of participants expecteed the target to be present, despite clear instruction

• 95% recalled the instructions

• 47% of incorrect witnesses would make same decision in real life

what is relative judgement?

deciding the person that looks most like the person in our memory

zajac also conducted a study looking at instruction bias they

• used 8-11yr children

• visited the police station

• confederate event

• varied lineup (TP orr TA)

• wild card on control

what was found?

wil card option increased childrens performance in target absent lineup

wild card option did not effect childrens performance in the target present line up

in wild card condition - target absent and target present accuracy rates did not differ

what are ways in which we can present the suspect to eyewitnesses?

live lineup vs photospread

simultaneous lineup

sequential line up

what is a simultaneous line up?

showing them all at once, comparing them

what is a sequential line up?

showing them one at a time - is it this person or not

simultaneous and sequential lineups are relevant to what type of judgement

sequential = absolute

simultaneous = relative

what is relative judgement

comparing them agaisnt each other, more liekly to pick someone but you should reject line up

sequential lineups result in what?

fewer identifications but fewer flase alarms

describe foil bias

choosing the foils for the lienup

bias lineup if the witness can pick out the suspect

police rig lineup so the suspect stands out

what is the backfire effect?

foils that are too dissimialr to the suspect may increase the chnaces of an innocent suspect being wrongly identified.

foils in a lineup that are too simialr will what?

confuse witness and increase the chances of a foil being identified

what constitutes optimal similarity ?

1. similarity to the witnesses verbal description

2. similarity to the suspect

clark and tunnicliff conducted a study where participants were asked to give verbal descrition of perpetrator, what were the 3 types of line up?

1. target present, description-matched foils

2. target absent, description-matched foils

3. target absent, suspect-matched foils

how can the police officer conducting the lineup influence the eyewitnesses decision?

• facial gestures

• body movements

• verbal behaviour

phillips conducted a study lookign at single blinded and double blinded conditions in target absent lineups, whatw as found?

a lineup administrators knowledge of the suspects position in the lineup can increase false identification rates in cases where the suspect is innocent

especially likely in sequential lineups

double blinded should be used

what is a psotdiction variable?

measurable products that correlate with indetification accuracy in a non causal manner

describe the relationship between confidence and accuracy

not much of a relationship

do witnesses get less confident over time?

no more confident

what are the issues with the confidence accuracy relationship?

confidence tends to get stronger over time and over subsequent identifications

positive feedback increases confidence

and inflates retrospective reports of confidence and viewing conditions

show how should we get accuracy and confidence?

interview straight away and no positive feedback

describe response latency?

accurate witnesses may make their descisions more quickly than inaccurate witnesses

10-12 seconds - may differ across viewing conditions