Hall & Player

• Topic 2 focus


  The collection and processing of forensic evidence
• Studies for topic 2

  Hall and Player 2008.

  Dror et al 2005.

  Dror

  Miller.

  The ACE-V method.

  Kassin et al.
• Main study for topic 2

  Hall and player 2008
• Hall and player 2008 participants

  70 volunteer fingerprint experts working metro police fingerprint bureau. Experience ranging from 3 months to 30 years (mean of 11 years).
• Hall and Player (2008) aim


  To see if a written report of a crime could affect the fingerprint identification of a poor quality print by experts.

  To establish whether fingerprint experts would be emotionally affected by the circumstances of a case.
• Hall and Player 2008 procedure

  A fingerprint was scanned and supper-imposed onto the top right corner of a £50 note. 14 prints were made and compared to ensure consistency. Each participant was given 1 of the 14 prints. the fingerprints of the suspect, the crime scene examiners report and a sheet of paper giving the context of the crime. Participants took part in the study as part of their normal work day, could leave as they please and had all the equipment they would have normally.

  Half the participants were assigned to a low emotional context and the other half a high emotional context.

  Low emotional context = the report referred to an allegation of forgery, saying the suspect had tried to pay for goods with a forged £50 note.

  High emotional context - Report referred to an allegation of murder, saying the suspect had fired two shots at the victim before decamping.

  Participants had to fill in demographic information including where they worked and number of years experience, and identify weather they thought it was a;

  identification (match),

  not an identification,

  insufficient (not enough detail to undertake comparison),

  insufficient detail to establish identity.

  They also had to provide details of their observations and opinions, say whether they had referred to the crime scene information and if so weather they believe this affected their analysis.
• Hall and Player 2008 findings

  57/70 had read the crime scene report.

  Out of those who read it 52% of those in the high emotional context condition believed it had affected their decision, while 6% in the low emotional context believed it had affected their decision.

  However, it was found that there was no significant difference between the two groups int he judgements they made regarding the fingerprints.
• Hall and Player 2008 conclusions

  Emotional context did not affect the ability of fingerprint experts to make a decision when analysing fingerprints.
• Dror


  Top-down biases.

  When a fingerprint is unable to be analysed by a computer, humans have to do it themselves. This top down process can include biases that would override the objective decision making of the process. This could include;

  Observer or expectancy bias - where the expert anticipates the outcome as a result of information from the initial observer and therefore has preconceived expectations of the outcome.

  
  

  Selective attention - Prior expectation can cause experts to filter out ambiguous elements in a partial print.

  
  

  Conformity effect - If the expert is being asked to validate another experts decision they may unconsciously be bias to agree.

  
  

  Need/determination bias - Bias arriving from a strong desire to solve a particular crime.

  
  

  Overconfidence bias - Experts may experience overconfidence and think they are always right even if there is contradictory evidence.
• Dror et al 2005

  27 student volunteers (8 males and 18 females)

  96 pairs of fingerprints were selected, half contained obvious bottom up info, so easy to decide is prints were a match. 48 pairs were not as clear.

  Two emotional states, high and low.

  Low = Cases with no harm to a person

  High = Cases where V was seriously harm or died.

  Subliminal priming condition use 'same' or 'guilty'

  It was found where the photos were ambiguous participants were swayed by emotional context.
• Miller


  Presented student subjects with either a hair sample from one suspect to match to evidence based on the principle of an identity line up, where they were given 5 hair samples from 5 different suspects to compare.

  This has been shown to reduce the number of false positive identification. This method is called a 'sixpack
• The ACE-V Method


  An acronym that stands for analysis, comparison, evaluation, verification. It is a scientific method for examination and documentation of latent finger prints.

  Analysis - Examiner assess the unknown print to determine if it is suitable for comparison or not.

  Comparison - Investigator analyses characteristic attributes of the fingerprints and identifies conformities between the known and found latent prints.

  Evaluation - Examiner is asked if there are any conformities between the revealed and known print and if there is a sufficient number of minutiae to identify the unique correlation. It is then concluded to be identified or individualised, not identified or excluded, inconclusive.

  Verification - The conclusion then needs to be verified by peer review.
• Kassin et al


  Proposed that examiners of fingerprints should work in a linear approach, rather then a circular way. They should progress from the crime scene evidence to comparison with a target rather then exploring these together or alternatively.

  Also suggests examiners should be unaware of crime scene information, including whether the suspect has confessed or not and they should not be in contact with any of the victims or their families.

  The varifier should be blind to both the case facts and conclusions of the examiner.