Crim Psych Topic 2: Collection and processing of forensic evidence

Question 1

Key Research - Hall and Player

Answer 1

Aims:
does the report of a crime affect a fingerprint experts identified? Are fingerprint experts emotionally affected by the circumstance of the case?

Sample:
70 fingerprint experts from the met police were used and their mean experience was 11 years

Procedure:
- participants had to look at a $50 note that had a fingerprint transposed onto it. The fingerprint was delibaretly ambiguous and not clear
- their job was to see if a set of fingerprints matched the print on the $50 note
- half the participants were told the fingerprints was from a suspect who tried to pay for goods with a fraud note: low emotion group
- half the participants were told that the note belonged to someone suspected of murder by firing gunshots.: high emotion group
- participants were offered a crime scene report but they could choose whether they read it or not
- after they filled in a questionnaire which asked them whether or not they had referred to the crime scene information

Results:
- 57 out of 70 of the participants said they had read the crime scene report and 30 were in the high-emotional context condition
- 52% of the 30 who read the report in the high emotional context condition said they believed it had influenced their decision

Conclusions:
the authors concluded that this study suggests that emotional context did not detract from the fingerprints expert capacity to make a final decision

Question 2

Dror - topdown biases

Answer 2

Bottom-Up Approaches: use examination of the ridges and patterns of the fingerprints to identify the unique features

Top-Down Approaches: use the experts experience and knowledge to make an assumption about the identity

top down is open to mistakes from aspects of the experts personality, emotional state and expectations

when top-down processing is used, it can reduce accuracy of analysis bias can affect cognitive interpretation

Question 3

Dror et al

Answer 3

• 27 uni students were given 96 pairs of fingerprints. Their task was to compare each print.
• half the fingerprints were clear and relatively easy to match and the other half was ambiguous
• when participants were shown high emotional cases, they were more likely to find a match between fingerprints compared to low emotional cases.
• when showed a message of guilty the results rise and this suggests that emotional context influence fingerprint analysis.

Question 4

Linear Sequential Unmasking

Answer 4

They look at the fingerprint from the crime scene, then look at the suspects prints, then back to the crime scene print looking for points of comparisons and can change their analysis

LSU APPROACH:
1. analyse the crime scene print on its own while recording unique features
2. extra information can be given when necessary in order of importance to the case to help make comparisons
3. experts can then revisit and add to their analysis

Question 5

Miller - the ‘six-pack’ idea

Answer 5

This involves comparing the evidence from the crime scene against a line up of 5 hairs. This showed reduce bias as they don’t know which sample is from the suspect
- to investigate the filler method, miller got a sample of student hair analysts and split them into two groups
- one group used the standard method
- those using the 6-pack method made fewer false positives 3.8% vs 30.4%