Criminal psychology-Topic 2 (Hall and Player (Results (Were they affected…
Criminal psychology-Topic 2
DNA can be found in saliva, blood, sweat, semen and hair. 'Touch DNA ' can be found on surfaces contacted by the perpetrator.
Forensic DNA analysis was introduced in the late 1980s/early 1990's. The first DNA-based conviction in the US was in 1987, when Tommy Lee Andrews was convicted of rape.
Real world example: In 2001, Gary Ridgeway was arrested and charged with serial murders of women after re-examination with new DNA technology found Ridgeway to be a match
First investigated by Sir Francis Galton in the late 1800's
Fingerprints leave a trace of the pattern on surfaces we touch (latent mark). One of the most common methods for collecting prints is by dusting a smooth surface with fingerprint powder (aluminium flake). If they appear, they are photographed. Unfortunately fingerprints can often be poor quality, smudged, distorted or incomplete-making analysis difficult and subjective.
Three types of fingerprints
iinvisible and need to be processed with powders or chemicals to be seen
visible to the eye because the person who left them had something on their fingers when they touched the surface.
these are impressions, they are created when someone touches a soft substance and they leave the impression of their fingerprint in the substance.
Real world example: In 2008, preschool teacher was victim, Donald Smith was arrested but it was his identical twin brother Ronald who did the crime.
Motivating factors and biases in collection of forensic evidence
Dror found a lack of consistency between fingerprint analysis. I tis possible that the decision could be influenced by motivating factors and bias when expert in processing the forensic evidence.
Motivating factors are things that influence the experts decision. This can happen when the fingerprint is poor quality, incomplete, smudged etc therefore more subjective.
Motivating factors are:
Emotional context of the case:
if the case has a high emotional context (murder etc) it could bias the expert more than if the crime has a low emotional context (theft)
Characteristics of the victim:
is the victim seen as particularly vulnerable (child, elderly etc) this could create bias in the expert
Pressure the expert feels they are under to solve the case:
if the case is classed as 'serious' or 'long running' the expert may feel more susceptible to bias
Satisfaction related to catching criminals:
this satisfaction felt by the experts when they 'solve' a case may increase the likelihood of bias. Satisfaction may be higher for cases classed as serious, long-running or high profile.
Hall and Player
To see if trained fingerprint experts are affected by the emotional context of a case. Secondly, to see if the written report supplied would affect an experts interpretation of a poor quality mark.
Field experiment. Independent measures design. Participants were randomly allocated to their condition:
1) Low emotional context- allegation of forgery, left the scene when confronted
2) High emotional context- allegation of murder, when confronted the suspect shot the victim before leaving.
A self selected sample of 70 fingerprint experts all working for the Metropolitan police fingerprint bureau. The mean length of experience of expert was 11 years. The majority were active practitioners
Fingerprint inked onto paper, background of note obscured the ridge detail so was poor quality print. Participants were given a latent print and a 10-print fingerprint form. Asked to consider if print was a match, not a match or insufficient detail. Then asked if they had referred to the crime scene report. Allowed to use a magnifying glass. Encouraged to follow their normal routines and no time limit. Told not to discuss case with anyone.
Were they affected by the emotional context?
of participants had read the crime scene report prior to examination. 52% of the participants who read the
scenario said they were affected by the information read. Only
Did this affect their judgements? NO.
no significant difference
between the final decisions made by the two groups.
emotional context has no effect
on the experts final options about a fingerprint match. Fingerprint experts are able to deal with the fingerprint analysis in an objective matter.
Working in isolation (blind testing):-
Involves removing details of the crime that may not be needed for an accurate fingerprint match. Includes being kept unaware of the crime-scene information. This technique can reduce the emotional context of the case.
This technique involves evidence from the crime scene being analysed before the expert learns of the profiles of any suspects. Unmask the info when/if needed.
Filler control method:-
Dror suggested that experts could be given a series of 6 comparison prints (similar to a line up). The task would not then simply be deciding if the latent print matches the comparison, but if it matches any comparison prints
Involves two independent fingerprint experts analysing the same prints, done in isolation from one another. Experts should be aware of who the other expert is and what they concluded. If the findings are inconclusive then further analysis would be needed.