Criminal topic 2 - the collection and processing of forensic evidence

Question 1

(Background) - bottom up processes

Answer 1

a latent fingerprint is compared with the databases fingerprint of the suspect

Question 2

(Background) - top-down processes

Answer 2

• contextual effects, such as experts’ prior knowledge and experience as well as their expectations and emotions
• can include confirmation bias that overrides the most objective decision-making of the bottom-up processors

Question 3

(Background) - Dror’s cognitive biases

Answer 3

~ Expectancy bias - analyse information that confirms preexisting assumptions. When the expert anticipates the outcome due to their expectations.
~ selective attention - small matches between prints. This expectation can lead to the ‘filtering out’ of ambiguous elements.
~ Need - determination bias - unconscious bias, ‘rational’ decisions are often based on emotional context, from a strong desire to solve the crime.

Question 4

(Background) - Dror’s experiment

Answer 4

aim: whether high emotional context increases the likelihood of a ‘match’ decision being made with an ambiguous pair.
sample: university students
conclusion: create a need - determination bias, as the more emotive the context the more motivated participants were to find a match.

Question 5

Key research - Hall and Player - aim, sample, procedure

Answer 5

aim: fingerprint experts were emotionally affected by the case details in the report, causing a bias in the report
sample: 70 fingerprint experts worked for the metropolitan police fingerprint bureau.
- experience from 3 months to 30 years
- self - selected
procedure: ambiguous latent fingerprint created and superimposed on £50 note
- each given test mark card, 10 print fingerprints and the scene examiner’s report.

Question 6

Key research - Hall and Player - procedure continued

Answer 6

• given the same tools to magnify the print
• randomly allocated to high (murder case) or low (a forgery case) emotional context group
  DV’s were:
• expert read crime scene examiners’ reports before examining fingerprint
• what verdict was - identification or not identification
• inconclusive or insufficient evidence to make a judgement
• whether they would be confident to present the fingerprint evidence in court

Question 7

Key research - Hall and Player - results

Answer 7

• only 57/70 experts read report
• high - identification - 6/35
• high - insufficient - 15/35
• low - identification - 7/35
• low - insufficient - 12/35
• confidnece in court - most said no due to ambiguity, no significant differecne between conditions

Question 8

Key research - Hall and Player - evaluations

Answer 8

Strengths:
- control of variables
- standardised - increasing reliability
- free will
- high usefulness - forensic application/ justice system
Weaknesses:
- low internal validity - knew they weren’t dealing with ‘live mark’
- demand charcateristics
- not representative of the general populations as they did this everyday
- ethnocentric and biased
- reduced usefulness - only for fingerprint analysis

Question 9

Application - strategies to reduce errors - caused by cognitive bias (Kassin et al)

Answer 9

• More education is needed to point out the subjective nature and vulnerabilities to bias.
• reduce the likelihood of bias from blind testing
• linear, rather than circular analysis needed
• filler control method - if there is one comparison, it could leas to the belief that they had committed the crime.

Question 10

Application - Miller

Answer 10

• presented students with either one hair from a suspect to match one found at a crime scene
• The second way reduces the likelihood of false positive identification as an analyst working ‘blind’ to the information which belongs to the suspect

Question 11

Application - Kassin

Answer 11

• analysts should be blind to the context of the crime and all surrounding information