Topic 2- collection of evidence

• Dror


  • bottom-up approaches- use examination of the ridges and patterns of the fingerprints to identify the unique features of each print to see if they match
  • top-down approaches- use the expert's previous experience and knowledge to make an assumption about the identify of the fingerprints
  • the top-down approach that is open to mistakes from aspects of the expert's personality, emotional state and expectations
  • examples of top-down cognitive biases include: expectancy bias, selective attention, conformity effect and overconfidence bias
• Dror et al


  • 27 university students were given 96 pairs of fingerprints. their task was to compare each finger print to it's pair
  • half the fingerprints were clear and relatively easy to match, the other half were ambiguous
  • some crimes were low emotion and others were high emotion, photos were used to reinforce each type
  • results showed that when participants were shown high emotional cases they were more likely to find a match between fingerprints compared to the low emotional cases
  • this suggests that an emotional context influences fingerprint analysis.
• Miller- 'six-pack' idea


  • instead of fingerprints, Miller looked at hair sample analysis
  • he found that hair experts were susceptible to need determination bias when matching a hair at a crime scene to a suspect's hair- saying the evidence matches to get a 'result'
  • Miller suggests the use of a similar method to a police line-up could reduce bias
• Linear sequential unmasking


  • normally fingerprint analysts are given two prints to compare
  • they look at the fingerprint from the crime scene, then look at the suspect's prints, then back to the crime scene print looking for points of comparison and can change their analysis throughout the process

  the LSU approach is:

  • analyse the crime scene print on its own
  • later, extra information will be given in order of importance
  • the expert can then revisit and add to his/her analysis but cannot delete or make changes to initial interpretations
• Hall and Player- sample 


  • 70 fingerprint experts from the Metropolitan police were used. their mean experience was 11 years
  • half the participants were told the fingerprint tried to pay for goods with a forged note, this is a low emotion group
  • half the participants were told the note belonged to someone suspected of firing two gunshots, this is a high emotion group
• Hall and Player- procedure


  • participants had to look at a £50 note that had a deliberately ambiguous fingerprint transposed onto it
  • their job was to see if set of fingerprints matched the print on the note
  • after analysing the fingerprint on the note the participants had to choose if the fingerprints matched, did not match, there was not enough detail or some agreement
  • participants also completed a questionnaire of how and why they came to their decision and they also recorded if they read the crime report
• Hall and Player- results and conclusion


  • there was no significant difference between the high and low emotion groups
  • this is the opposite of Dror's study
  • emotional context does not reduce a fingerprint experts ability to make a final decision
  • many of the experts choose not to read the crime report- suggests they are capable of analysing fingerprints in a objective manner