Crime topic 2 Flashcards
What did miller suggests about hair samples?
In the same way a line up is used for visual identification of a suspect, a similar procedure should be used for analysing hair samples - less likely to produce false positives
What did miller do?
gave some students 1 sample from 1 suspect and some 5 samples from 5 suspects to match to evidence (known as a six pack
What was the aim of Hall and Player’s study?
To see whether 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
What was the sample of Hall and Player’s study?
70 volunteer fingerprint experts working for the MET police Fingerprint Bureau - range of experience (3 months-30 years - mean 11 years)
What were the findings of Hall and Player’s study?
57/70 had red the crime scene report - of those who read the report, 52% in the high emotional context believed it had affected their decision, while 6% in the low emotional context
Despite this, their decision actually hadn’t been affected as there was no significance found between the two groups in terms of their judgements
What was the conclusion of Hall and Player’s study?
Emotional context did not affect the ability of fingerprint experts to make a decision when analysing fingerprints
What were the low and high emotional contexts of Hall and Player’s study?
low - examiner’s report referred to an allegation of murder, saying that the suspect had ‘tried to pay for goods with a forged £50 note’
High - Examiner’s report referred to an allegation of murder, saying that the ‘suspect then fired two shots at victim before decamping’
What did the participants have to answer in their questionnaire?
Fill in demographic information including where they worked and number of years’ experience, and to identify whether they thought it was:
- Identification (match)
- Not an identification (match)
- 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, which part, and if they thought the information had affected their analysis
What actually happened in the procedure of Hall and Player’s study?
Each participant given 1 of 14 prints, the relevant 10-print fingerprint form from the suspect, the crime scene examiners report, and a sheet of paper advising the participants of the context
They all took part as part of their normal working day. E.g. they had no time limit and could come and go as they wanted . They had access to a fingerprint magnifying glass and a russel comparator
what were the results of Miller’s study?
The group using the six-pack made less false positives when matching the hairs
What are bottom up approaches according to Dror?
examination of the ridges and patterns of the fingerprints to identify the unique features of a person - the first process - but if prints are degraded or incomplete, then the examiner must adopt the second process
What are top down approaches according to Dror?
When contextual effects impact how decisions on a match are made and the expert uses previous experience and knowledge to make an assumption about the identity of the fingerprints
What were the four biases outlined by Dror?
Observer or expectance bias
Selective attention
Conformity effect
Overconfidence bias
What Is observer or expectancy bias?
Expert anticipates an outcome due to information from an initial observer and therefore has preconceived expectations about the outcome
What is selective attention bias?
filtering out of ambiguous elements in a partial or ambiguous print where a close call has to be made to create a match
What is conformity effect in terms of fingerprint analysis?
If a fingerprint expert is asked to validate the decision of a peer or superior, this may unconsciously effect them to agree with the original decision
What is overconficence bias?
May make experts believe they are always right, even in the face of contradictory evidence
what is need-determination perception?
From a strong desire to solve a particular crime
What was the sample of Dror’s 2005 study?
27 university students (9 males and 18 females) - mean age of 23
What were the results of Dror’s 2005 study?
When shown high emotional cases, they were more likely to find a match between fingerprints (58%) compared to the low emtional cases (49%)
When the subliminal messages were added to the emotional cases (49%)
What did the results of Dror’s 2005 study suggest?
emotional context does influence fingerprint analysis
What was the procedure of Dror’s 2005 study?
press a button for either same or different to indicate whether they thought the fingerprints were matched
In some emotional cases - subliminal messages including the words “same” or “guilty” were flashed up on the screen
96 pairs of fingerprints were selected - they contained obvious bottom up information - half contained more ambiguous info, to top down info would be required
Outline Linear Sequential Unmasking?
Expert must first examine and document the trace evidence from the crime scene before being exposed to the known referencer material such as the case report - presented as late as possible and only when necessary
Outline the LSU in terms of the examiner’s reports
it allows them to add to their initial analysis but prevents them from removing or deleting from it - they can also specify their confidence levels about fingerprint identification that my help in understanding the degree to which judgement about trace evidence were changed following exposure to reference material
