criminal psychology - collection and processing of evidence Flashcards
what is forensic evidence
information collected from a crime scene
what are strengths of using fingerprints as forensic evidence
unique and can be used in court as evidence
thought to be objective
what is an example of a real life error when using fingerprints as evidence
Madrid bombing- latent fingerprints left on bag
suspect identified as Brandon Mayfield who was 1 of 20 matches but had been person of interest since 9/11
protested innocence until police found real suspect
what is bottom up processing
Data driven and uses physical detail of actual fingerprint such as overall pattern of ridges
more objective
what is top down processing
uses contextual elements to help analyse
e.g experts knowledge and experience
what is the background research for this topic
Dror -2005
what was the aim of drors 2005 study
what are the effects of top down processing
what was the procedure of drors 2005 study
ps asked to analyse 96 good quality or poor quality fingerprints and also given emotional stimuli (case details on either bike theft or murder) with photos
what was the findings from drors 2005 study
when fingerprint quality was poor they relied more on contextual information
ps were affected by emotional context
what was the conclusion from drors 2005 study
where the match of the prints was ambigous the decisions of the participant were swayed by emotional context by top down contextual clues
what is the background to hall and players study
hall and player wanted to investigate whether real fingerprint experts would be affected by emotional context of crime scene report as students were in previous research
what was the aim of hall and players study
to investigate whether fingerprint experts are emotionally affected by the circumstances of a case
what is the sample in hall and players study
70 participants from metropolitan police
mean length of experience 11 years
independant measures and volunteer sampling
allocated to either high or low emotional context- 35 in each condition
what is the procedure in hall and players study
ps given £50 note with superimposed fingerprint - told to treat task as part of normal working day
given a magnifying glass and a russell comparator to help them compare
asked whether fingerprints were
match
not match
insufficient
and to elaborate on findings to gain qualitative and quantitave data
completed feedback sheet which asked if they had referred to crime scene report and if they felt like it had impacted their analysis
what were the findings from hall and players study
no significant difference found between two conditions on number of matches - emotional context had not affected outcome
52% of ps in high emotional context condition felt they were affected by information
6% in low emotional context condition felt like crime scene report had influenced decision
19% didnt read crime scene report
what are the conclusions from hall and players study
didnt find evidence to support previous research
experts though they were affected but werent possibly due to experience?
how can fingerprints line ups reduce bias in processing of forensic evidence and what is the evidence
providing fingerprint analysts with multiple similiar possible comparisons e.g fillers means examiner would be more blind to information which may belong to suspect
evidence- miller : asked students to compare hair from crime scene against either a single hair or a line up of three hairs
30% misjudged when only shown one hair
4% misjudged when shown 3 hairs
how can blind testing reduce bias in processing of forensic evidence and what is the evidence
expert shouldnt be aware of any information about crime or who has previously examined the prints
evidence - dror asked experts to analyse a set of prints they had previously identified as a match and told they had been mistakenly matched by FBI
all but one changed original identification
how can sequential unmasking help to reduce bias in processing of forensic evidence and what is the evidence
examiner has info revealed to them as and when they need it
evidence - hall and player participants felt as though evidence may have slightly affected them
drors students also felt as though evidence had affected them
