The collection and processing of Forensic Evidence Flashcards
What is one motivating factor and bias when experts are collecting evidence?
Finger print experts are emotionally driven and motivated which can an impact on the final results.
Who researched into motivations of workers?
Charlton
What sample did Charlton use?
Interviewed 13 fingerprint experts from a variety of law enforcement agencies
What did Charlton find?
Their main motivations were job satisfaction, satisfaction of catching the criminal and solving cases and solving high profile cases.
What is another example of finger print experts being motivated by emotions?
The Brandon Mayfield Case.
A brief summary of what happened during the Brandon Mayfield Case.
There was a train bombing in Madrid which killed 191 people and injured 1800. A fingerprint left n the bag was matched to Brandon who was a recently Muslim convert. All experts agreed the fingerprint was his, until Spanish police found that it wasn’t.
What are the three categories of cognitive bias?
Expectation bias, Confirmation bias and contextual bias.
What is expectation bias?
Where the expectations of what have happened affects what is actually happened.
What is confirmation bias?
People test hypotheses by looking for confirming evidence rather than for potentially conflicting evidence.
What is contextual bias?
When someone has other info aside from that being considered which influences the outcome of that decision. E.g finding out they are finding evidence for a murder apose to a bike being stolen.
Who researched into the effects of contextual biases?
Dror.
What sample did Dror use?
27 university volunteers with a mean age of 23.
What were the ppts in Dror sample manipulated by?
Providing background info including disturbing images.
What was the sample of 27 split by?
Either having a clear fingerprint or having a more ambiguous and less clear (more representative of real life).
What two types of emotional states were used?
Either a high emotional context like murder or a serious attack, or a low emotional context crime like a theft of a bike.
What was the DV in Dror’s study?
They were measured on how many matches were made.
What is a piece of quantitative data which can be found in Dror’s study?
In the unambiguous condition matches were unaffected by context. As, in the ambiguous condition, 58% were matched in the high emotional context condition, compared to 49% in the low condition.
Who was the key researcher for this section?
Hall and Player.
What did Hall and Player aim to investigate?
H+P aimed to test if context affected fingerprint identification by fingerprint experts.
What are two controls that made the experiment as naturalistic as possible?
They were asked to participate at their normal working hours and could stay or go as they pleased.
What was the IV in H+P research?
Whether the ppts was in a high context or a low context scenario.
What were the 3 DV’s in H+P research?
Whether the ppt had read the crime report or not, whether the ppts matched the fingerprint and whether they were confident or not to prevent the evidence in court.
What sample was used in H+P research?
70 fingerprint experts who worked for the Metropolitan police with the mean length of experience at 11 years.
What was the fingerprint in H+P research printed onto?
A £50 bank note
How many were in the low context group and what was on their examination report?
35 ppts with a scenario relating to forgery.
How many were in the high context group and what was on their examination report?
35 ppts with a scenario of a murder.
What were ppts in H+P research then asked to do?
Asked to compare the fingerprint with another 10 fingerprints with an examiners report.
After completing the experiment, what question were they asked on the feedback sheet?
Asked if they felt their judgement had been affected by the examination report.
What statistics were found about the crime report?
57/70 had read the crime report with 30 in the high context group and 27 in the low context group.
For those who had read the high context, how many felt affected compared to the low context?
52% said they felt affected compared to 6% in the low context scenario.
What was not found in the results with a stat to back it up?
The context dd not effect the professionals decision making as 6 in the high group saw the fingerprint as identification and only 7 in the low context group.
What is the first technique which reduces expectation bias?
The latent mark should be analysed independently before analysing the comparison print.
A piece of research to to back up comparing the latent mark independently?
Dror.
What did Dror find?
Found that fingerprint examiners differed in reliability. As they found that if the comparison was viewed first, fewer key prints of the latent print.
What was another application made to do with reducing context effects?
The fingerprint expert should be blind to any crime evidence.
Who researched into combating contextual bias?
Dror.
What did Dror find about context and crime?
The more matches were made with more emotional crime details.
