Collection + Processing Of Forensic Evidence (biological) Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

what does forensic evidence refer to

A
  • Fingerprints
  • DNA evidence from hair, skin cells etc.
  • Bite marks
  • Blood spatter analysis
  • Evidence from computer hard drives etc.
  • Evidence from footprints or tyre prints
  • Fibres from clothing etc.
  • Ballistics
    refers to any evidence that is collected from sources other than
    self-report from a victim, perpetrator or witness.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

collection of evidence

A

All forensic evidence can still be subject to bias. Fingerprint analysis (which have been used at crime scenes for over 100 years) have been shown to be affected by this bias, particularly following the high profile case of Brandon Mayfield.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Hampikan et al. (2011)

A

Hampikan et al. (2011) reviewed transcripts of a number of wrongful
convictions and found that forensic evidence was involved variety of ways:
- 38% contained incorrect blood analysis
- 22% contained incorrect hair comparisons
- 3% contained incorrect bite mark identifications
- 2% contained incorrect fingerprint identifications

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Motivating factors and bias in the collection

A
  • Charlton et al (2010) interviewed 13 fingerprint analysts and produced and in-depth description of their main motives. They summarised them as:
  • Rewards (job satisfaction linked to skills)
  • Hope and Satisfaction linked to catching the criminal and solving the case
  • Factors linked to case importance (seriousness and length of time passed)
  • Feelings associated with searching for and finding matches
  • The need for closure
  • Fear about making mistakes.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Dror et al. (2011)

A
  • 2 analysts used when analysing fingerprints to prevent bias as they are usually unclear when collected.
  • Dror et al. (2011) found discrepancies between analysts when looking at same finger prints, + also when 1 analyst looked at same finger prints on multiple occasions (low intra- rater and inter-rater reliability)
  • One reason for this, is range of cognitive factors which can bias decisions.
  • Comparing fingerprints is an information-processing task + involves processes such as attention and visual searching. Pertinent information could sometimes draw a persons attention and irrelevant information could distract them.
  • Attention and emotion may cause interpretation changes
  • As finger mark clarity decreases interpretation can become more
    difficult and subjective and therefore open to bias. - Instead of relying on tested scientific methods, the process is mostly based on the subjective beliefs of the analyst, and if there is pressure to find an offender, errors are more likely to occur.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what factors effect bias

A
  • The type of crime
  • The nature of the victim
  • The nature of the suspect
  • The type of photos included in the file
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

problems with fingerprint analysis

A

Subjective contours can distort data so we can think we see things which aren’t there. Thus, a fingerprint analyst may see a contour or ridge which actually isn’t there, especially if actively trying to find point of match.
There is some evidence that experience may help, but even those who are most experienced can still have issues as a result of “circular reasoning” – that once some points of similarity are found, others are then “found” (imagined) to support them.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

hall + player aim

A

In the UK fingerprint examiners are provided with a copy of the crime scene report, (which details the nature of the crime)
- Hall and Player thought it was important to determine if these practices introduce an emotional bias:
The study aimed to investigate whether:
> Fingerprint experts were emotionally affected by the case details?
> Does emotional context bias the judgements of expert analysts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

hall + player sample

A
  • 70 participants, all working for the Metropolitan police fingerprint bureau, responded to a request for volunteers to take part in an experiment. The request did not give details of the experiment.
  • Their length of experience as experts ranged from less than three months to over 30 years. The mean length of experience was 11 years.
  • 12 had managerial roles and although were still on the UK National Register of fingerprint experts, they were no longer active practitioners.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

further sample

A
  • To make sure the experts decision was accurate a finger mark from a known source was made. A volunteer’s forefinger was inked and introduced to a piece of paper. A ten print test card was also produced to be given to the analysts as comparison prints.
  • This good quality clear mark was then super-imposed on a scanned image of a £50 note, positioned so the background obscured some detail. The mark was then manipulated to control the contrast and further obscure.
  • A separate sample confirmed the fingermark was of poor quality and ambiguous.
  • The clarity, size and quality was representative of prints they would normally receive.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

groups in hall + player

A

Ppts asked to treat experiment as they would a typical day, they could come and go as they pleased, and talk among themselves as long as they did not discuss the finger mark or the experiment itself. No time limit was placed on the participants.They were assigned to one of two groups:
- The low-context group (35 participants) given an examination report referring to an allegation of forgery. chosen as it is considered a victimless crime and carries a relatively minor sentence.
- The high-context group (35 participants) was given an examination report referring to an allegation of murder. This was chosen because there is, inevitably, a victim and it carries the most severe sentence.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

key info

A

The experts were then asked to consider whether the mark was
- An identification (a match)
- not an identification (not a match)
- insufficient—not enough detail to undertake a comparison,
- insufficient detail to establish identity, some detail in agreement but not enough to individualise.
asked to elaborate on findings by providing observations and opinions. also asked whether they had referred to the crime scene report and if they had, had it affected them.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

methodof hall + player

A

Experiment – (although designed to be as naturalistic as possible as it took place in work time, in a typical fingerprint examination room, elements of control were used including analysts could not seek advice from each other.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

IV of hall + player

A

whether the participant was allocated to the low-context or the high context group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

DV of hall + player

A

Whether the participant considered the finger mark was;
- identification – a match,
- not an identification – not a match
- insufficient – not enough detail to undertake a comparison,
- insufficient detail to establish identity, some detail in agreement but not enough to individualise;
Whether the participant read the crime scene examination report prior to examining the fingerprint. Whether the participant would be confident to present the fingerprint as evidence at court.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

results

A
  • 57 of the 70 participants (81.4%) had read the crime scene examination report prior to examining the prints.
  • 52% of the 35 who had read the high-context scenario felt that they were affected by the information given on the examination report, compared to only 6% in the low-context scenario, indicating there is a relationship between the type of context and the perceived effect on the experts.
17
Q
A

Identification - Insufficient - Insufficient - No identification
High-context 6 15 13 1

Low context 7 12 16 0

18
Q

Will the introduction of an emotional context affect fingerprint analysis & decision making

A

χ²= 0.94; df = 1; p=>0.05
- There is no significant difference in the willingness to present analysis in court between those in a high context and those in a low context

19
Q

conclusion

A
  • emotional context does affect the analysis of the finger print, but this has no effect on the outcome.
  • Experienced analysts are more resilient to emotions than non experts in Dror’s case
  • seems that the details of the crime are surplus to requirement, so it may be best not to provide them, so as to keep the process as objective as possible.
  • such analysis forms only part of the final information presented in court, which employs imaging technology that has ensured a good level of reliability for over 60 years.
20
Q

application 1- Educating detectives, judges and juries about the strengths + weaknesses of forensic science

A

portraying it as a scientific picture of the crime, but explaining that it is still vulnerable to bias as a result of its subjective nature. This might include recommending that the judge asks the forensic scientist presenting the evidence how much they knew about the case in advance.

21
Q

application 2 - Training forensic examiners to minimise bias

A

making them aware of the risk of bias, and that willpower alone cannot prevent it. Training could include knowledge of psychological factors such as perception, judgement & decision making.

22
Q

application 3 - Introducing appropriate protocols

A

sequential unmasking/blind testing– this could include limiting forensic analysts access to information about the case that is not absolutely necessary for them to reach a decision. This would make the decision more objective as this is a form of blind design. A similar process could be employed with a verifier – a second person who also analyses the evidence without the knowledge of the decision reached by the first