Hall & Player (2008) - Fingerprint analysis and decision making
Aim
Answer 2 questions
Does the written report of a crime, as routinely supplied with fingerprint evidence, affect a fingerprint expert's identification of poor quality print?
Are fingerprint experts emotionally affected by the circumstances of a case?
Background (DROR)
Participants
70 volunteer fingerprint experts work for the MET police
Experience range 3 months - 30 years (mean 11y)
58 active in teams, 12 managerial roles, not active practioners
Materials
Ambiguous fingerprint from known source (right forefinger) was superimposed on the corner of a 50 pound note
14 prints were made for use in the exp and compared to ensure consistency
Crime scene report
Method
Ps allocated to either 1 of low emo context / high emo context condition (independent measures design)
Ps received either low EC (forgery) or high EC (murder)
After examination asked to decide if mark was a match, not a match, insufficient (detail to make a comparison), or insufficient detail to establish identity (some detail was in agreement but not enough to individualise).
Also asked to provide details of their observations and opinions
Completed a feedback questionnaire which asked if they'd referred to the crime scene info and if they had, which part
If yes, asked to say how info had affected their analysis
Results
57/70 said they read crime scene report. 30 in high EC condition.
52% of the 30 said report has influenced their decisions, compared to 6 in low EC
Chi-squared shows no significant difference in outcome between 2 ECs.
Conclusion
EC did not distract fingerprint experts' capacity to make a final decision
2 ways of processing prints
Bottom up: Using actual details of the eye
Top-down: Using contextual elements e.g: prior knowledge, expectation, emotional state
Study on fingerprint experts
5 asked to see if they thought a latent print matched a print from a suspect
It was a pair they previously identified as a match 5 years earlier
Given expectations from experimenters that it's not match
1/5 identified as match. the rest gave different decision to their original (not a match/ insufficient data)
Study on students
Gave uni students good quality or poor quality/ambiguous print to study
Given emotional stimuli: low level (theft) and high level (murder) - with disturbing images of victims
Subjected to subliminal messages stating 'guilty' or 'same' during their initial analysis
Emotional context does interfere with analysis. More likely to identify ambiguous prints as matches.