PictureLisa Hall / Emma Player
ackground: Motivating factors and bias in the collection and processing of forensic evidence
Key Study: Hall and Player (2008) Will the introduction of an emotional context affect fingerprint analysis and decision-making?
Strategy: Reducing bias in the collection and processing of forensic evidence
Background: Motivating Factors
Charlton et al (2010) identified the main motives of fingerprint analysts;
  1. Expression of satisfaction with their job, skills and successful procedures or strategies
  2. Satisfaction with crime solving: catching criminals
  3. Satisfaction with crime solving: type of case (e.g. rape / murder)
  4. Feeling of getting a match
  5. Closure (give peace to victims and themselves) and
  6. Fear of error.
 
Background: Cognitive Biases
The Government has identified 6 cognitive biases that may affect the examination of forensic materials:
  1. Expectation bias
  2. Confirmation bias (looking for confirming evidence rather than conflicting evidence)
  3. Anchoring effects (relying too heavily on initial information)
  4. Contextual bias (other information aside from that being considered)
  5. Role effects (identifying themselves within judicial systems)
  6. Reconstructive effects (when people rely on memory rather than taking detailed notes).
Hall and Player (2008) Will the introduction of an emotional context affect fingerprint analysis and decision- making?
Previous research and context to the study
  • The role of the fingerprint expert is to see if the friction ridge detail in a set of fingerprints is ‘sufficiently similar’ to that found at a crime scene
  • Fingerprints can sometimes be of poor quality so judgements can be subjective
  • Early research focused on how emotional context can impact upon decision-making. This research is limited in applicability as it involved non-expert samples.
 
Aims
  • To see if trained fingerprint experts are affected by the emotional context of a case.
  • To see if the written report supplied with fingerprint would affect an expert’s interpretation
 
Method/Design
Field experiment with an Independent measures design, random allocation:
  1. Low emotional context – allegation of forgery (victimless crime)
  2. High emotional context – allegation of murder.
 
Participants
  • Self-selecting sample of 70 fingerprint experts all working for Met Police Fingerprint Bureau
  • The mean length of experience as a Fingerprint Expert was 11 years
  • Majority were active practitioners, with the minority no longer active (e.g. in a managerial role).
 
Procedure
  • Fingerprint (right forefinger) from a volunteer inked onto paper and scanned onto a £50 note
  • Background of note obscured the ridge detail - fingerprint=poor quality
  • Participants provided with an envelope with one of the test marks, a 10-print fingerprint form, and a sheet of paper telling them that the print was of the right forefinger
  • Ps asked to consider if the print was a match / not a match / insufficient detail to decide
  • Ps asked if they had referred to the crime scene report and if it had affected their analysis.
 
Results
  • 57/70 read the crime scene examination report prior to examining the prints. Thirty of these were from the high-context scenario group
  • 52% of the 30 Ps from the ‘high emotional context’ scenario who read the crime scene report said they were affected by it. Significantly different from the 6% in the other group
  • No significant difference between the decisions made by the 2 groups
  • No significant difference between the 2 groups as to whether the experts would feel confident in presenting the evidence in court.
 
Conclusions
  • Emotional context has no effect on the experts’ final opinions about a fingerprint match
  • Fingerprint experts are able to deal with the fingerprint analysis in a non-emotional manner
  • Further research needed e.g. length of service and type of crime.
Blinding precautions
  • Give forensic examiner only the information that is required to do an effective examination
  • How: only give the fingerprint or biological sample, remove all context from the report given to  expect forensic teams to work in a different location than the police
  • Hall and Player: stops context being introduced, which could provoke a cognitive bias (such as an expectation bias)
 
Blind verification
  • Require another independent examiner to check the material without knowing the conclusions of the 1st examiner
  • How: make sure 2 people independently give their decision on the forensic evidence
  • Why: Minimises the risk of confirmation bias
  • Charlton – minimises the risk of motivating factors such as satisfaction with crime solving.