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The Collection and Processing of Forensic Evidence (Biological) - Coggle…
The Collection and Processing of Forensic Evidence (Biological)
Motivating factors and bias in the collection and processing of forensic evidence
Motivating factors and forensic evidence
Strongest motivating factors is reward when complete part of investigation that leads to crime being solved
Need to bring investigation to close (cognitive closure)
Emotional motivation in fingerprint analysis:
Charlton (2010) investigated whether apparent presence of emotions in fingerprint examination would influence fingerprint analysis
Qualitative approach using semi-structured interviews with 13 experienced fingerprint experts from variety of law enforcement agencies
Asked 'How did you feel about succeeding in matching prints?'
Reward of job satisfaction
Satisfactioon associated with working serious/long cases
Emotional feelings associated with need for closure
Emotions linked to making mistakes and finding identification matches
Influence of crime type on emotions:
Dror et al (2005) manipulated high/low emotional contexts from either violent or non-violent crimes with 27 student volunteers
Ps given information and had to match fingerprints that were either ambiguous or unambiguous
Significant interaction between stimuli type and top-down manipulation
Need for cognitive closure:
Motivator because of psychological need to bring decision-making process to definitive conclusion
Kruglanski (2006) -> when cognitive closure need high, quicker judgements made and with more confidence
When cognitive closure need low, more possibilities considered and better decision-making occurs
High profile cases -> more errors made -> unfounded confidence paradox
Biases and forensic evidence
Tversky and Kahneman (1974) -> human decision making not as rational as believed to be
When systematic and unintentional errors made -> called cognitive bias
Made lead to error in judgement
Contextual bias:
Irrelevant contextual information influences reasoning
E.g. if fingerprint poor quality, more likely to be used in serious crime than less serious
E.g. prior knowledge of state of arrested person -> may cause focus on them instead of others
Confirmation bias:
When people look for or interpret information to confirm their pre-existing beliefs/assumptions
Occurs when requests for fingerprint examinations happen
Role effects:
Role effects occur when experts identify themselves within judicial systems, may cause subconscious bias
Integrated automated fingerprint identification system (IAFIS):
Using this, examiners become used to accepting fingerprint at top of list as correct
IAFIS results returned in order of relevance
Increased risk of cognitive bias
Types of forensic evidence
Fingerprints:
Unique patterns so successful use as means of identification -> reliable
Bottom up and top down processing:
Bottom up -> data driven, take individual elements e.g. pattern of ridges
Top down -> look at contextual factors (bigger picture) for final decision
Hall and Player (2008) on Fingerprint Analysis
Background and aims
Analysis and comparison of fingerprints relies on ability to recognise similarities/differences between ridge details of fingerprint
Fingerprint experts still capable of error -> identification must be verified before reported
As clarity decreases, subjectivity increases
Aims:
Does the written report of a crime as routinely supplied with fingerprint evidence, affect a fingerprint expert's interpretation of a poor quality mark?
Are the fingerprint experts emotionally affected by the circumstances of the case (i.e. affected by the context of emotion)?
Method
Field experiment, IV = whether ps experienced high or low emotional context, DV = ps were asked:
Whether print was a match, not a match, insufficient or insufficient detail to establish identity
Whether or not they referred to crime scene examination prior to assessment of prints
Whether they felt information in examination affected their analysis and whether p would present as evidence in court
Sample:
Self selected of 70 experts from Met police fingerprint bureau. Mean experience 11 years
Procedure
Ps asked to work in work time in a typical fingerprint examination room in New Scotland Yard Bureau
Tasks given to each group:
Low emotional context -> suspect try to pay with forged £50, decamped
High emotional context -> suspect did previous and then fired two shots at victim before decamping
Ps given envelope with fingerprint and asked if any match with suspects
Post experiment questionnaire:
Ps finished experiment, completed demographic information sheet
Given feedback sheet -> whether they referred to report prior to assessment or not and if so, indicate what information was read
If report referred to, did it affect their analysis
Materials:
Volunteer's right fore finger impression on £50 note. 14 copies made using cannon laser 1000 printer
Ps given envelope with one of 14 prints, one 10-print fingerprint form, crime scene report
Allowed magnifying glass and Russell comparator
Results
Effect of written report:
57/70 read report prior to examining prints
30/57 were high emotional context
52% of 30 felt they were affected by information in report
6% in low emotional context felt affected by information in report
Conclusions
If experts think serious crime-type influenced analysis, outcome not affected
Less affected by cognitive bias than those in Dror et al (2005)
Some (19%) didn't read report, so unaware of context of fingerprint when making judgements
Strategies for reducing bias in the collection and processing of forensic evidence
ACE-V
Analysis, comparison, evaluation and verification (ACE-V) is structured approach to fingerprint identification, used to minimalise bias
Analysis phase:
Latent print examined to determine ovcerall ridge pattern, then maginifaction used to examine details
Assessment of all various causes of distortion and effect on clarity of print
Comparison phase:
Examiner concentrates on the known, inked prints
Each print examined observing all details for consistent image with latent print
Evaluation phase:
Prints examined side by side, finds features in first and looks for in second
Verification phase:
All positive identification opinions must be verified by second expert -> must do so blind
Linear sequential unmasking (LSU)
Forensic examiners should work linear, not circular to prevent bias
What is LSU?
Expert must examine and document trace evidence first from crime scene before seeing case report
The process of LSU:
After initial analysis, sequential unmasking approach ensures other case information is presented as late as possible in process
E.g. expert may make initial analysis, then given case report, should only be used to help make identification
An example of LSU (Dror et al 2015):
Important to impose limits on when examiners allowed to revisit/alter initial analysis
LSU allowed examiners to add to initial analysis but not remove or delete from it
Specify confidence of fingerprint identification that my help in understanding degree to which judgements change after seeing report
Evaluation
Nature/nurture
Nature:
Analysts have inbuilt biases that cause errors that they make
Emotional motivation innate?
Freewill/determinism
Hard determinism:
Confirmation bias -> always looking to confirm view -> built into us
Soft determinism:
Confirmation bias but trained to consider everything
Training makes them think independently
Freewill:
Analysis asked if information affected their judgement
Reductionism/holism
Reductionist:
Bias is cognitive in nature -> all cognitive
All evidence is biological
Holistic:
Not just forensic evidence, also witness statements (eg)
Many different types of forensic evidence collected
Individual/situational