2. COLLECTING AND PROCESSING FORENSIC EVIDENCE Flashcards
Bottom-up
Refer to database
Top-down
Use own awareness of crime
Expectancy bias
Expert anticipates outcome
Selective attention
Section that matches previous data/evidence
Need-determination bias
Strong desire to solve crimes, may rush analysis
Aim of Dror
Investigate whether high emotion context increases likelihood of a match decision
Dror sample
Uni students
Dror method
Lab
Dror procedure
Given pairs of fingerprint images See if they matched Manipulated crime context (murder= high emotion, theft= low) Manipulated image (neutral= table lamp, graphic= knife wound on face)
Results from Dror
When crime context involved harm= more likely to say ambiguous pairs matched
What does Drors research suggest
Need determination bias is created as Ps are more motivated to find match in high emotion context
Pros of Dror
Controlled (C+E)
Standardised (replicable)
Quantitative data (objective)
Useful applications- remove context from analysis
Cons of Dror
Lacks population validity (uni students)
Reduced ecological validity- no consequences of wrongful match
Demand characteristics
Hall and Player aim
Experts from MET fingerprint Bureau show a bias for matching ambiguous prints in high emotion context
H+P sample
70 experts
3 months- 30 years experience
Self selected
H+P method
Lab
Independent
H+P procedure
Deliberately obscure fingerprints on $50 note
Latent print= only just identifiable and an ambiguous match confirmed by other experts
IV- high (murder) or low (forgery) emotion case
DV:
1. did expert read report before matching?
2. did they identify a match?
3. would they be prepared to present in court?
H+P results
Very few matches
57/70 read report
High emotion condition- experts affected by report
No link between emotion and analysis of print
most not confident to present in court
What does H+P research suggest
Emotional context plays role in feelings, but doesn’t produce top-down processing bias
Experts better than non-experts
Don’t provide context for real life cases
Pros of H+P
Useful applications- don't provide context High population validity- experts Controlled- same equipment Standardised Independent- reduces DC
Cons of H+P
Less generalisable (same type of people) Lacks ecological validity- no consequences Demand characteristics
