topic 2 the collection and processing of forensic evidence Flashcards
what is the key study and the four additional studies of topic to criminal called
Hall and Player
-Dror-top down biases
-Dror- research with 27 students
-Linear sequential unmasking
-Miller
Outline the additional study by Dror on top down biases
False identification- 2004 A number of different experts identified Mayfields fingerprint on a bag ( a man linked to madrid bombings- it was not him)
BOTTOM UP APPROACH
-use examination of the ridges and patterns of fingerprints, without knowing anything else
Top down approach
-use the experts previous experience and knowledge to make an assumption about the identity of the fingerprints
Conclusion
-Top down approach is more open to mistakes from the experts personality, emotional state and expectations
Application
-experts should look at fingerprints out of context so that there is no conformation? emotional bias
Outline the additional study carried out by Dror- research with 27 students
Sample
- 27 university students were given 96 pairs of fingerprints to judge as a match or not
-Half the pairs were c;ear and the other half were unclear and ambiguous
Low emotional context- a description of the crime was given which didnt involve any harm to anyone
High emotional context-a description of the crime was given which involves harm e.g murder assault
Photos were shown to reinforce context and in some cases the words ‘same’ and ‘guilty’ would flash up onto the screen.
Participants then had to hit a button, one being that the fingerprnints were a match and the others that they werent a match
The emotional context significantly impacted judgements for the ambiguous prints
Matching rate:
low emotional context 49%
high emotional context 58%
subliminal message 66%
Outline the aditional study by Miller on the six pack idea
1) analyse the crime scene print
2)given suspect print along with 5 other dummy prints (fillers/foils) that are a bit like the suspects print
3)Miller tested this with students being given either 1 hair sample to compare or 5 hair samples plus the suspect one to match
Conclusion
Miller found that it is less likely to produce false positives if there are a false 5 (misidentification)
Outline the additional study on Linear sequential unmasking (LSU)
1)look at the latent print (crime scene) print first and make judgements/ notes which you can add to later but NOT DELETE
2)look at the suspect print and do the same thing seperately
3)Then if need be look at any additional information about the crime, only need information that may help e.g what the print was on
4)revisit notes and information for points of comparison but do not delete anything
What was the key study of topic 2 crimanal psychology called
Hall and Player
What was the background to Hall and Player
-Dror and other research had fond that some people were bias in their fingerprint analysis. For example when there is a high emotional context
Can you name 5 cognitive biases
-Expectancy bias
-Selective attenyion bias
-Conformity bias
-Needs determination effect
-Overconfidence bias
Outline what is meant by Expectancy bias
When the expert expects there to be a match between prints because of information from an intial observer. (For example a police officer asking to identify this person as the suspect as they have been identified by a witness)
Outline what is meant by Selective attention bias
Filtering out ambiguous details such and only docusing on the features that match
Outline what is meant by Conformity effect
When asked to validate the opinion of another expert , they may be unconsciously biased to agree with the decision
Outline what is meant by Needs determinayion effect
The desire to solve a particukarly emotional crime may lead to high motivation to find a suspect and therefore errors being made about whether the prints matched or not
Outline what is meant by Overconfidence bias
-Being an expert may make them overconfident about their own judgement and therefore overlook evidence that proves tham wrong
Outline the aims of the key research by Hall and Player
- Does the written report of a crime, as routinely supplied with fingerprint experts effect a fingerprint experts identification of a poor quality print
-are fingerprint experts emotionallu effected by the circumstances of the case
Outline the sample of the key research by Hall and Player
-70 volunteer fingerprint experts for the metropolitan police
-average experience of 11 years
-58/70 were active in teams dealing with a full range of crimes
-12/70 were in maagerial roles
Outline the equipment used in Hall and Players key research
-volunteers right forefinger was inked and printed onto paper. It was then superimposed onto a £50 note with the detail of the note obscuring ridge detail- ambiguous
-14 prints were made for use in the experiment
Each participant was given:
- one of the 14 printed fingerprint marks on a 50£ note
-the relevant ten fingerprints from the suspect
-the crime scene examination report
-a sheet of paper advising the context + inclusing the information that it was done withe the right forefinger
Outline the procedure of the key research by Hall and Player
- All participants took part of it as part of their normal working day and tested in a typical fingerprint analysis room. They were each given a fingerprint magnifying glass and a russel comparitor. They were told to act as if it was a normal working day, but they could not discuss the prints they were analysing. There was no time limit.
-The research was conducted anonymously and half the participants were assigned to one condition half to the other
What were the 2 conditions fingerprint analysis experts were in Hall and Player
Low emotional context
-given an examination report referring to an allogation of forgery. A victimless and relatively minor crime. e.g Tried to by goods with fake £50 note
High emotional context
-an examination report referring to an allegation of murder. Chosen as a victim and severe sentece e.g ‘suspect then shot two gunshots at vixtim before decamping’
Fingerprint analysis experts in Hall and Player had to decide if the fingerprintwas
1)identification (a match)
2)not an identification (not a match)
3) insufficient (not enough evidence to compare
4)insufficient detail to establish identity (some similarities but not enough)
They were also asked to elaborate by providing details f their observations and opinions
Finally they completed a specially designed feedback questionnare which asked them whether or not they had reffered to the crime scene information
What were the results from the key research by Hall and Player
57/70 said they read the crime scene report 30 of these were in the high emotional context condition
52% of the 30 in the high emotional context condition said they believed it had influenced their decision, compared with only 6% of the low emotional context condition
What statistical test was carried out and was there a significant difference in the key research by Hall and Player
Chi squared test
There was found to be no significant difference between the two conditions of high and low emotional context
What was the conclusion of the key study by Hall and Player
The emotional context does not detract from the fingerprint experts capacity to make a final decision
Explain one application of the key study by Hall and Player
- Attend regular training events so that they are up to date with regular practice and ways of avoiding bias
- Regular training would include how to follow the bottom up approach when carrying out analysis and what they can do to verify a print
- This can be shown by Dror study into bottom down approaches
