The collection and processing of forensic evidence (biological) Flashcards
What is the type of evidence that should be collected from a crime scene?
- DNA
- hair sample
- fingerprints
- footprints
- dental records
- blood samples
- trace evidence
- weapon
- victim / body
What is the key piece of forensic evidence for this topic?
fingerprints
What is fingerprint analysis?
human beings analysing the ridges and furrows that make up a fingerprint (unique to each person)
What is the downside to fingerprint analysis?
not free from human error and subjectivity
What is the system that is used to analyse fingerprints?
ACE-V
What does ACE-V stand for?
Analyse
Compare
Experts
Verify
How long have fingerprints been used?
over 100 years
What does the length of time that fingerprints have been used for suggest about the method?
very reliable and effective
What is a key piece of evidence that goes against the use of fingerprint analysis?
the Brandon mayfield case
What is the Brandon mayfield case?
a man falsely accused of a series of bombings in Madrid - due to multiple people (including his own lawyer) falsely identifying a fingerprint match
How often are fingerprints misidentified?
2% of the time
Who is the key background researcher?
Dror
What does Dror suggest?
that fingerprints are too subjective and due to human examiners (human error)
What is confirmation bias?
intentionally looking for evidence that would validate their current beliefs
What are bottom-up processes?
purely data driven - more objective
- examination of ridges
- examination of patterns
- ‘zooming in’ - uniquely identifiable features
What are top-down processes?
contextual factors that influence whether a match is made or not (more subjective)
- experiences
- expectations
- pre-conceived ideas
How many cognitive biases are there?
5
What are the 5 cognitive biases?
- observer or expectancy bias
- selective attention
- conformity effect
- need-determination perception
- overconfidence bias
what is observer or expectancy bias?
when the expert anticipates the outcome of the match as a result of information from another observer, therefore has as pre-conceived idea of whether a print is a match or not
What is selective attention?
focusing on the ridge details so that they can match rather than ones they cannot match due to expectations
What is conformity effect?
if an expert is asked to validate a match that has already been made by another expert, this may lead them to agree, unconsciously, with the original decision, especially if with a peer or superior
What is need-determination perception?
when there is a strong desire or urgency to solve a crime such as serial killers
What is overconfidence bias?
having more experience experts will be more confident and are more likely to believe they are right
What was Dror’s 2006 background research?
- five volunteer fingerprint experts - unfamiliar with the Mayfield case
- treated as a normal working day
- prints used = definite matches from 5 years earlier in their own careers
- context manipulated & given expectations that it would NOT be a match
What were the results of Dror’s 2006 background research?
- only one participant (20% / 1/5 ) agreed with original decision (a definite match)
- 80% of participants contradicted original decision
- 60% of participants completely contradicted original decision - declaring definite non-match
What were the conclusions of Dror’s 2006 background research?
- failure of fingerprint experts to give reliable decisions
- affected by contextual information
- confirmation bias
What was Dror’s 2005 background research?
- subliminal priming (unconsciously taking in messages)
- 27 uni students
- good quality or incomplete (poor) quality fingerprints to study - reflected real life cases (ecological validity)
- subliminal messages = ‘guilty’ or ‘same’ during initial analysis
What were the results of Dror’s 2005 background research?
- control condition = 47%
- low emotional context = 49%
- high emotional context = 58%
- high emotional context (+ subliminal priming) = 66%
What did Dror’s 2005 background research conclude?
where the match of the prints was ambiguous the decisions of the student participants were swayed by emotional context (top-down)
