Crime: Topic #2 = Forensic Evidence - Bio. Flashcards
Full title: The collection and processing of forensic evidence (biological).
What is forensic evidence?
Evidence obtained often from the crime scene by scientific methods.
E.g., ballistics, blood test, DNA test.
(Used in court as evidence).
-> Helps to establish to guilt or innocence of possible suspects.
What are types of forensic evidence?
-> Forensic anthropologists
Examine human remains.
= age, gender, height, injuries, estimated time of death,
-> Forensic dentists
Examine teeth
= Help identify a person
-> Detecting and identifying controlled substances involved in a crime
-> Computers
Used for committing crime
Police = use them to fight crime. (Digital evidence).
-> Microbiomes
Communities of microorganisms that live on or in people, plants, soil, oceans & atmosphere.
= indicator of time-since-death / link victims to different areas / link to human DNA.
-> Forensic DNA analysis
Used since late 1980s.
= generate a DNA profile of an individual
= uses samples: blood, bone, hair etc.
MOST COMMON:
-> Impression evidence
-> Pattern evidence
-> Forensic toxicology
Analysis of biological samples for the presence of toxins e.g., drugs.
= Information: type & amount of substances present in an individual
-> Trace evidence
E.g., fibres, hair, soil, wood, gunshot residue, pollen etc.
= transferred between people, objects & environment during a crime.
= Link a suspect and victim to location.
Impression evidence definition
Typically either:
2-dimensional E.g., fingerprint.
OR
3-dimensional E.g., marks on a bullet caused by the barrel of a firearm.
Pattern evidence definition
Additional identifiable information found within an impression.
E.g., an examiner will compare shoeprint evidence with several shoe-sole patterns to identify a brand / size etc.
Fingerprint analysis
Overview
-> Used for over 100 years
To provide accurate info.
-> Different / unique
No 2 fingerprints have ever been found alike (in billions).
-> The basis for criminal history foundation at every police agency.
-> Most commonly used forensic evidence
Why are fingerprints (analysis) used over other analysis?
Why is it better?
Other visible human characteristics e.g., facial features tend to change with age.
Fingerprints are relatively persistent.
The Fingerprint Branch
Overview
E.g.:
-> Name
-> Location
-> Created / history / how
-> Repository / size
NAME:
First created (1974):
National Society of Fingerprint Officers.
Renamed (1977):
The Fingerprint Society
LOCATION:
New Scotland Yard (Metropolitan Police)
CREATED:
July 1901
USING:
The Henry System of Fingerprint Classification.
1974:
4 employees o Hertfordshire Fingerprint Bureau contacted fingerprint experts throughout the UK and began organisation of the first professional fingerprint organisation.
Initially consisted of only UK experts but expanded to international.
Initials F.F.S behind a fingerprint expert’s name indicates they are:
Fellow of the Fingerprint Society.
INTERPOL’s Automated Fingerprint Identification System repository exceeds 150,000 sets of fingerprints from 190 member countries.
What are the different types of fingerprints?
/ ridge patterns?
& how common?
1-Loops: 60%
2-Whorls: 35%
3-Arches: 5%
When do ‘motivating factors’ exist?
Motivating factors often exits when:
experts investigate crimes that have high emotional context, such as murder and violent attacks. This increased level of emotion creates a strong desire (motivation) to find the offender.
The false arrest for the 2004 Madrid bombings.
Summarise!
1- Brandon Mayfield
Had already raised suspicion form the American police due to being connected / suspected (not ever convicted) with the 9/11 bombings.
2- Wrongfully detained
In connection with the 2004 Madrid train bombings because of a (incorrect) fingerprint match.
3- Arrested
On May 6 2004, was arrested by FBI as a material witness & held him for 2 weeks before releasing him w/ a public apology (following Spanish authorities identifying another suspect).
4- True suspect
Instead, Ouhnane Daoud = true suspect, and his fingerprints were a closer match to the fingerprint found on a bag containing the detonating devices.
What did Kassin et al (2013) argue?
That there is proof that such errors could be made and that forensic science is not infallible.
(Such errors = Wrong suspect - 2004 Madrid train bombing)
Why do fingerprint errors occur?
(e.g., identifying wrong suspect)
Cognitive neuroscientist investigated.
Itiel Dror
Believed: HUMAN ERROR
We use a human expert to make the final judgement.
Explains through cognitive bias.
Outline:
Cognitive psychology assumption / approach
1- “Our brains are like a computer”
They input, process, store, and output information.
2- Believes
Our behaviour is influenced by cognitive processes.
E.g., language and memory.
Key studies:
- Loftus & Palmer: Leading Qs
- Grant et al.: Context dependent memory
What studies can be used to link to fingerprint identification & why?
Fingerprint Identification:
1- Loftus & Palmer
= Leading Questions
-> Witness
-> Influences to unconsciously find matches to existing.
2- Grant et al.
= Context dependent memory
-> Can be affected by emotional context
-> How likely are to say fingerprints are a match.
What study can help explain the errors (fingerprint identification) made?
Dror (2012)
= Cognitive bias
-> Errors in thinking
Contextual bias definition
Occurs when irrelevant contextual information about an event, or the way in which information is presented, influences reasoning.
Experts can be affected by details:
-> The crime
-> The background of the suspect.
Example:
-> Prior knowledge of the status of an arrested person.
-> Lead to a particular focus on that individual
-> 2004 bombings / Dror
What is confirmation bias?
The tendency to interpret new evidence as confirmation of one’s existing belief or theories.
E.g., Dror: convinced it was Brandon Mayfield so subconsciously influenced the match).
What were the types of processes in fingerprint matching that Dror (2005) identified?
1- Bottom up
2- Top-down
What is:
Bottom up (fingerprint matching)?
Purely data driven.
Look at the individual elements e.g., pattern of ridges and specific individual features.
-> Unaffected by bias - clear print
What is:
Top-down (fingerprint matching)?
Starts from a broader picture, LOOKING AT THE LARGER CONTEXTUAL FEATURES that affect the final decision.
E.g., emotional state of the expert, their level of experience, context of the investigation.
-> Bias - partial / unclear / smudged print.
What did Dror (2006):
-> suggest
-> find
Suggest:
Context could also bias decisions and lead to errors being made.
Found:
Confirmation bias affected the fingerprint analysis of the participants.
What was Dror (2005)’s:
-> aim?
-> Conclusion?
-> Used to suggest?
AIM:
To investigate how a particularly emotional case context affects how likely people are to match fingerprints.
‘People’: university students - not experts
Fingerprint matching: Top-down process
CONCLUSION:
Emotional context (top-down) = can influence analysis of fingerprints in ambiguous prints.
SUGGEST TO EXPERTS:
Don’t show fingerprint analyst’s the crime so emotional context doesn’t influence.
CAN’T: Used students so emotion may have influenced more because not experienced / fully trained.
What was Hall & Player (2008)’s
-> Aim?
-> Participants
-> IV & DV
-> Conclusion
AIM(S):
1- To investigate if the fingerprint experts were emotionally affected by the case details in the report.
2- To investigate if the emotional context would bias the judgement of expert analysis (as in Dror).
PARTICIPANTS:
70 volunteer fingerprint experts (3mnths - 30 years experience) working for the Metropolitan Police.
IV:
Low / high emotional context
DV:
Whether Ps felt affected by the scenario / affected their decision and judge of the print.
CONCLUSION:
Emotional context did not bias their decision making, and that ‘experts are more adept at dealing with fingerprint analysis in a non-emotional detached manner than non-experts’.
Application
What can be done to help reduce cognitive bias in fingerprint experts?
If the experts are shown the crime scene report prior to matching the fingerprints, as suggested by Hall & Player’s study the should:
Receive proper training which educates them about all following a strict protocol (help reduce cognitive bias).
What strategies did Dror (2012) and Kassin (2013) suggest?
(NOT KEY EVIDENCE <- H&P INSTEAD)
1- Education
Point out forensic science’s subjective nature.
2- Training
Learn to acknowledge and minimise bias. Cognitive expoerts to train practitioners.
3- Sequential unmasking
Follow protocols and procedures, ensure irrelevent information is filtered out. Focus on bottom up.
4- Blind testing
When asking to verify a decision they shoud not be aware of initial conclusion and the identity of the examiner (should avoid conformity bias).
5- Searching for the negative
Rather than trying to match, try to mismatch.
6- Filler-control method
(Like the blind testing)
Instead of being given 1 sample print for comparison
Application
What does ACE-V stand for?
Analysis, comparison, evaluation and verification.
Application
What is ACE-V?
-> What
-> Where used
-> Involves
WHAT:
A trusted approach to fingerprint identification which can be useful in minimising the effects of bias.
USED:
Used widely in the UK & US
INVOLVES:
There are 4 steps.
What does the ACE-V involve?
There are 4 steps:
1- Analysis phase
2- Comparison phase
3- Evaluation phase
4- Verification phase
What do the 4 steps from ACE-V entail?
1- Analysis phase
2- Comparison phase
3- Evaluation phase
4- Verification phase
1- Analysis phase
An examiner analyses the fingerprint / mark.
2- Comparison phase
The examiner then compares the mark to a known print.
(Analysis phase can be revisited here).
3- Evaluation phase
Having compared the images, the examiner evaluates what they have seen and reaches a decision.
4- Verification phase
The results are then subject to verification by one additional examiner or more.
Why is the ACE-V useful?
1- STRUCTURED
Provides a structured approach for experts to follow
2- ACCURACY
Allows for cross checking to determine accuracy.
3- PRESENTING EVIDENCE IN COURT
The information can be trusted and a fair trial can take place.
Why is the ACE-V effective?
1- Scientific approach
2- Reduces bias
The fact that a blind verification process takes place leaves the initial identification open to peer review and reduces the chances of bias.
What does LSU stand for?
Linear sequential unmasking
What is LSU?
The expert must first examine and document the trace evidence from the crime scene before being exposed to the case report.
What is the process of LSU?
Following the trace evidence, other case information is presented as late as possible and only when necessary.
They may also be given information about the complexity of the crime, but this should only be given to help if needed.
An example of LSU?
Dror 2015
LSU allows examiners to add their initial analysis but prevents them from removing or deleting from it.
Experts can also specify their confidence levels.
Why is LSU useful?
1- Interpretation
Means that the trace evidence should be interpreted in the same way regardless of any suspect they may have.
2- Reduces bias
Also offers reasonable restrictions that reduce bias, whilst not effecting the expects ability to investigate.
Why is LSU effective?
Dror (2012) suggests a cost-benefit analysis.
The decision to provide case information to an examiner, must be based on the contribution it would make and the potential bias.
E.g., the more difficult the case, the most an expert may be susceptible to contextual effects.
