Component 3: Crime - Forensic Evidence

Question 1

What happened in the case of Brandon Mayfield?

Answer 1

11th March 2004 a series of bombs went off on 4 commuter trains in Madrid. 191 people were killed and a further 1800 people were wounded.
A latent finger print was lifted from a bag believed to belong to the bomber which contained detonating devices. Using the standard FBI protocol, Brandon Mayfield was identified. This protocol inlcuded having anumber of fingerprint experts examine the fingerprint and all agreed the prints were Mayfields. He protested his innocence.
The Spanish police matched the print to the real bomber Ouhnane Daod.

Question 2

What is cognitive bias?

Answer 2

Fingerprint experts make their own judgements not a machine in terms of if eveidence is a match or not.

Question 3

What is confirmation bias?

Answer 3

A form of cognitive bias that occurs when people intentionally seek specific evidence in order validate their opinions. This bias makes people more likely to ignore other evidence that could contradict their beliefs.

Question 4

What two fingerprint matching techniques does Dror describe?

Answer 4

Bottom- up processes and top-down processes

Question 5

What is the bottom-down process of fingerorint matching and what are the weaknesses?

Answer 5

Purely data driven
Examination of overall pattern of friction ridges
Examination of characteristics of specific ridges
‘Zooming in’ to examine thinsg such as location and distribution of sweat pores, individual ridge technology and other uniquely identifiable features.
In the real world, prints are often poor quality and are only partial prints meaning their is insufficient evidence to match a print.

Question 6

What is the top-down process to fingerprint matching and what are the weaknesses?

Answer 6

This refers to how contextual effects influence how decisions are made. E.g. experts prior knowledge, expectations and emotional state. This means the process can include biases that override objective decision making.

Question 7

What are the problems with fingerprint analysis?

Answer 7

There is a lack of consistency in fingerprint analysis.
Dror et al found that individual fingerprint analysts differed from one another (inter-observer consistency) and from themselves over time (intra-observer consistency)

Question 8

What is the conformity effect?

Answer 8

if a fingerprint expert is asked to validate the decision of a peer/superior this may unconsciously bias them to agree with the original decision.

Question 9

What is the observer/expectancy bias?

Answer 9

This is when the expert anticipates the outcome because of information froman initial observer and therefore, has preconcieved expectations about the outcome.

Question 10

What is selective attention?

Answer 10

Prior expectation can lead to the ‘filtering’ out of unclear elements in partial prints where a ‘close call’ must be made to create a match

Question 11

What is the need-determination effect?

Answer 11

This bias occurs from a strong desire to solve a particular crime. E.g. serious long running cases

Question 12

What emotional motivation in fingerprint analysis?

Answer 12

Reward of job satisfaction, including pride in using their skill.
Satisfaction associated with catching criminals.
Satisfaction associated with working on serious, long running cases.
Emotional feelings associated with the need for closure.
Emotions linked to making mistakes and finding identification matches.

Question 13

How does crime type influence emotions on finegrprint experts?

Answer 13

Dror manipulated low and high emotional contexts using pictures and stories from either a violent or non-violent crime with 27 student volunteers. They then had to match fingerprints that were eitehr ambiguous or unambiguous. They took the top-down approach and were influenced by the emotional circumstances of the case.

Question 14

How does the need for cognitive closure effect fingerprint experts?

Answer 14

Fingerprint experts are motivated to make a firm identification so that their part of the criminal investigation is complete. When the need for closure is high, quicker judgements are made and with more confidence. When the need for closure is lower, larger number of possibilities are considered and better decision making occurs.

Question 15

What is contextual bias?

Answer 15

Fingerprint experts can be influenced by the details of a crime and background of the suspect.

Question 16

What were the aims of Hall and Player’s research?

Answer 16

1. Does the written report of a crime, as routinely supplied with the fingerprint evidence, affect a fingerprint expert’s interpretation of a poor quality mark?
2. Are fingerprint experts emotionally affected by the circumstances of the case.

Question 17

Describe the sample in Hall and Player’s research.

Answer 17

70 fingerprint experts who worked for the Metropolitan Police Fingerprint Beaureu who volunteered to take part in an experiment. The request did not detail the experiment. The length of experience ranged from less than three months to over 30 years. The mean length of experience was 11 years. The majority were active practitioners with only 12 no longer being active practitioners.

Question 18

What was the research method of Hall and Player’s study?

Answer 18

Lab experiment/field experiment
IV - low emotional context or high emotional context
DV - whether the print was a match, not a match or insufficient, whether or not they had referred to a crime scene examination report prior to their assessment and whether in their own judgement, they felt the information in the report affected their analysis and if so would they be confident to present the fingerprint as eveidence in court.

Question 19

What was the procedure of Hall and Player’s study?

Answer 19

In order to create an environment that was as naturalistic as possible, they all participated during work time and in a typical fingerprint examination room in New Scot;and Yard Fingerprint Bureau. They were told to treat it like a typical day and could talk to eachother, just not about the prints.
1. A fingerprint from a known source was scanned and superimposed onto an image of a £50 note to obscure most of the ridge detail.
2. A separate team of experts confirmed it was a poor quality print and an amiguous match to 10 prints.
3. Each participant was given an envelope with a test mark card, the 10 fingerprint form and a copy of the examiner’s report. They were told the fingerprint was from a forefinger to speed up the process.
4. Participants were randomly allocated to groups of 8 and asked to treat the case like an ordinary working day.
5. Participants were assigned to one of 2 IV conditions. Low emotional context (forgery - victimless crime) High Emotional context (muder case)
6. All had to give elaborate details on their findings. Via a feedback sheet, they were asked if they referred to the crime scene report and if they had done so, did the information influence their analysis.

Question 20

What were the results of Hall and Player’s study?

Answer 20

57/70 read the crime scene report and 30 of these were the high emotional context
52% of the 30 felt affected by the information compared to 6% of the low emotional context. This suggests a relationship between the type of context and the perceived effects on the experts.
The final decision made by the two emotional contexts was very similar so no significant difference was found.

Question 21

What were the conclusions of Hall and Player’s study?

Answer 21

Even if experts think that a serious crime-type influenced their analysis the final outcome is not affected

Question 22

How does training experts to acknowledge and minimise bias help?

Answer 22

Awareness of bias is an important step to dealing with it but it cannot be turned off and on by awareness alone. Training by cognitive experts could help practitioners minimise the influence of cognotive bias on their decisions. E.g. provide basic training in psychology that is relevent to forensic work such as aspects of perception, attention, judgement and decision-making.

Question 23

What is Linear Sequential Unmasking? (LSU)

Answer 23

The expert must first examine and document the trace evidence fron the crime scene before being exposed to the known reference material such as a case report.

Question 24

What is the process of LSU?

Answer 24

Following the initial analysis of trace evidence, the case information is presented as late as possible and only when necessary. It is gradually unmasked in sequence of importance to the case.

Question 25

What is the usefulness of LSU?

Answer 25

It is useful as it means that trace evidence should be interpreted in the same way regardless of any suspect who is considered as a possible source. It is also useful because it offers reasonable restrictions that reduces bias while providing examiners flexibility in forensic work. However, it does not prevent exposure to biasing relevent information.

Question 26

What is the effectiveness of LSU?

Answer 26

Dror demonstrates the effectiveness of LSU procedures using a cost-benefit analysis. The decision to provide case information must be based on the relative contribution it would make to the examiner’s work relative to the potential bias. An informed decision as to whether to expose or mask information has to be made and this should include factors such as the difficultly of the case, because the more difficult forensic decisions are the more susceptible to contextual effects.

Question 27

What are the practicalities of LSU?

Answer 27

Dror’s suggestion of addimg confidence assessments will require more care and work during analysis but it could provide clear benefits. It is also important to consider which and how many pieces of additional evidence should be given to examiners.