the collection and processing of forensic evidence Flashcards
how are fingerprints used?
have three specific classes from their visual appearance
what types of fingerprints are there?
arches, loops and whorls
what does 5% of the population have?
arches
what does 60% of the population have?
loops
what does 35% of the population have?
whorls
why do errors occur?
although it appears objective, it is still a human expert who makes the final decision on whether forensic evidence is a match or not
what can there be errors with?
fingerprints, blood evidence, hair comparisons and bite marks
how can these errors be explained?
cognitive bias and confirmation bias
what did dror (2011) find?
that different fingerprint examiners differ from one another and themselves over time
what did dror (2011) find about emotional context?
by adding the context of the crime/pressure, decision making can be easily affected by our emotional context. in a high emotional-context there is an increased likelihood of a match being made with an ambiguous print.
what was hall and player’s (2008) aim?
to see if emotional context would bias the judgement of expert analysts
what were hall and player’s (2008) participants?
70 qualified fingerprint experts working in london met police, and had average experience of 11 years.
what was hall and player’s (2008) design?
superimposed a fingerprint onto a £50 note on a card- which they ensured was ambiguous and poor quality from other experts’ confirmation. given a typical case report and told to treat it like a normal day- they were able to talk, but not about the task at hand.
what was hall and player’s (2008) IV?
low or high emotional context- randomly assigned to groups of 8
what was the low emotion condition?
crime was a forgery
what was the high emotion condition?
same report except for the last sentence, where the crime became a murder
what was hall and player’s (2008) DV?
whether the analysts reported feeling affected by the scenarios, and whether this affected their final decision about the fingermark
what were hall and player’s (2008) results?
only 57/70 participants read the crime scene report, 52% in the high-emotion context felt affected by it, and 6% in the low-emotion
however no significant differences were found in their decisions as they were professionals
what did hall and player’s (2008) conclude?
emotional context does affect experts’ feelings, but it does not influence the final outcome of their analysis. compared to dror’s study, this shows that fingerprint experts are better at doing analyses in a detatched manner than non-experts.
what was the issue with dror’s study?
used students, who were not experts
examples of debasing techniques in the collection of evidence
blinding precautions; independent checking
what are blinding precautions?
giving the forensic examiner only the necessary information to conduct an effective examination, which guards against contextual bias
what is independent checking?
the independent application of analysis, comparison and evaluation by another examiner who does not know the conclusions of the first examiner, which minimises the effect of confirmation/cognitive bias
