The collection and processing of forensic evidence (Biological)


The collection and processing of forensic (Biologi

Motivating factors and bias in the collection and preocessing of forensic evidence- 

e.g emotional factors, the need to get a result/ make a conviction, fingerprints, blood samples, boot/ shoe prints, tyre marks, hair/ fibre samples, DNA 

Forensic evidence: info gathered and analysed by forensic scientists. Forensic science is the application of science to criminal and civil laws. 

Key research: Hall and Player (2008): will the introduction of an emotional context affect fingerprint analysis and decision-making? 

Theories which study is based:

Analysis and comparison of fingerprints relies on the ability of an individual to recognise the differences of similarities between the ridge details of a fingermark obtained from a crime scene and one taken from a suspect- the process is open to the questioning of an expert's ability to accurately anaylyse and interpret friction ridges. 

Subjective and clarity decreases and as a consequence the expert is more vulnerable to external stimuli 

Experimental research suggests that emotional effects based on externl stimuli impact on decisio-making process during the examination of fingerprints (Dror 2005)

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Hall and Player (2008)- Context

UK- Training for a fingerprint expert involves a structured programme of formal courses, which teaches and assesses a series of competencies 

e.g, the scientific theories of foetal fingerprint development and the factors that give rise to their observed individuality; 

methods for the recovery of latent marks;

applied examination techniques, utilising analysis, comparison, evalutation and verifaction (ACE-V) methodology. 

Then have work experience 

Work is peer reviewed and assessed 

Marks available from a crime scene- often incomplete, smudged, distorted, rotated and obscured by the substrate. In order to secure quality, it is standard operating procedure for teh identification process to be conducted independently by at least 2 fingerprint experts. 

Been suggested that the circumstances surrounding a crime case and the pressure experts are put under to produce results may influence the reported outcome (Risinger 2002) 

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Hall and Player (2008)- Context (Dror- 2005)

Dror gave uni students either good quality or incomplete, poor quality fingerprints to study. They were also given emotional stmuli deemed low level (case details pertaining to a theft) or high level (case details pertaining to a murder). 

Results show that volunteers were affected by the emotional context and this interfered with their decisions, making them more likely to make matches or identifications when analysis poor quality pairs of fingerprints. 

This research raised the questions:

a) would the same results be found with trained fingerprint experts?

b) are mis-identifications due to emotional bias

Hall and Player thought is was important to ascertain whether the normal working practices employed by the Metropolita Police Fingerprint Bureau introduce emotional bias. 

they designed research to answer whether; a) 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?

b) are fingerprint experts emotionally affected by the circumstances of the case? 

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Hall and Player (2008)- Research Method

Lab experiment

Independent measures design 

Designed to be as naturalistic as possible; ppts asked to participate in work time, in typical fingerprint analysis room within New Scotland Yard Fingerprint Bureau. 

Task itself was artificially generated and participants were randomly allocated to one of the two conditions. 

The experts weren't allowed to ask eachother for their opinions, whereas in a naturalistic setting there would be no capacity to stop this.

IV: low-context or high-context group 

DV: a) whether ppt read the crime scene examination report 

b) whether the ppt considered the fingerprint was (i) identification- a match (ii) not an identification- not a match, (iii) insuffucient detail to establish identity, some detail in agreement byt not enough to individualise, 

c) whether the ppt was confident to present the fingerprint as evidence in court. 

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Hall and Player (2008)- Procedure

Ppts were all respondents to a request for volunteers. Didn't go into detail of the experiment.

70 fingerprint experts working for the Metropolitan Police Fingerprint Bureau took part. Thier length of experience as experts ranged from less that 3 months to 30+ years. 

Materials- a finger impression from a well known source was used. A volunteer's rigth forefinger was inked and introduced to a piece of paper- good quality, clear mark scanned onto computer and superimposed onto an image of a £50 note. 

All 14 copies of the mark were compared to ensure consistency.

Each participant allowed access to a fingerprint magnifying glass and a Russel compacter 

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Collection of evidence (Cognitive)

Collection and the use of evidence from witnesses and suspects:

for example, identity parades, identikits (photo-fits, E-fits). the difference between an interview and an interrogation, the Reis technique's 9 steps of interrogation, interviews (the standard interview, the cognitive interview- CI, the stuctured interview- SI, the enhanced cognitive interview- ECI) 

Retrieval techniques used in cognitive interview:

context reinstatement

in-depth reporting 

narrative re-ordering 

reporting from different perspectives

Enhanced cognitive interview:

greet and personalise the interview and establish rapport, explain the aims of the interview, initiate a free rapport, compatible questioning, varied and extensive retrieval, investigateively important questions, summary, closure, evaluation

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Hall and Player (2008)- Procedure

volunteers assigned into groups of 8. 

asked to treat experiment as they would a typical day 

No time limit

participants assigned one of two groups, low-emotional or high-emotional context 

Low-emotion context group given an examination report for forgery, other group- murder

Asked to consider whether the mark was:

identification (a match)/not an identification (not a match)

insufficient (not enough detail to undertake a comparison)

or insuffient detail to establish identity.

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Hall and Player (2008)- Key findings & Conclusions

57/70 ppts indicated that they'd read the examination report pior to examining the prints. 

high-emotional context- 50% felt that they were affected by the information given 

Results show that the final decisions made by experts were similar, regardless of emotional context.

No relationship between emotional context and presenting the mark as evidence in judicial proceedings.

Shows how finger marks are open to interpretation 


Both emotional context and severity of a case affect a fingerprint expert's analysis but this doesn't have an effect on their final decisions. 

there may be motivating factors and bias in the collection and processing of forensic evidence


reducing bias- e.g educating detectives e.g by using 'filler-control- method to combat circular reasoning ans bias

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