1. 2. The Collection and Processing of Forensic Evidence
PREVIOUSLY WE LOOKED AT… WHAT MAKES A CRIMINAL
TODAY WE WILL LOOK AT… HOW WE ‘CATCH’ CRIMINALS

2. Imagine there is a crime, how can you know for certain who committed the crime?
Everyone has an individual finger print
Can you trust finger prints?

3. Brandon Mayfield
On March 11, 2004, Al-Qaeda-inspired terrorists coordinated a massive bombing of the Madrid commuter train system during rush hour
193 people were killed and around 1,800 were injured
Two fingerprints were recovered during the investigation on a bag of detonators by the Spanish national police
The prints were ran through the database and 20 possible matches were found for one finger print, one of whom was Brandon Mayfield
Brandon (a former US army platoon leader) was, at the time, an attorney specialising in child custody.
The police investigated his past where he…
Converted to Islam after meeting his wife
Represented one of the seven men who travelled to Afghanistan to fight for al Qaedea in a child custody case
Worshipped at the same mosque as the militants
Despite the finger print not being a full match he was falsely accused
Why do errors occur during finger print analysis?
This is what we will be looking at!

4. Forensic evidence = analysis of finger prints
Background: Motivating factors and bias in the collection and processing of forensic evidence
Key Research: Hall and Player (2008) Will the introduction of an emotional context affect finger print analysis and decision making
Application: Strategies for reducing bias in the collection and processing of forensic evidence 

5. Background: Motivating factors and bias in the collection and processing of forensic evidence
What is fingerprint analysis? The process involves looking at the ridge details of a fingerprint and deciding if they match another set of finger prints (fingerprint from crime scene; latent mark is compared with the suspects print; comparison print) Two fingerprint experts complete the identification process in order to verify the judgements made and reduce the likelihood of misidentification

6. Background: Motivating factors and bias in the collection and processing of forensic evidence
Finger print analysts
Psychology offers an insight into the motivating factors and biases that can affect the decision making involved in finger print analysis
Charlton et al. (2010) interviewed 13 finger print analysts and produced an in-depth description of their main motivates. These were summarised as:
Rewards (job satisfaction linked to skills)
Hope and satisfaction (linked to catching criminals and solving crimes)
Factors linked to case importance (importance or long running cases)
Feelings associated with searching for and finding matches
Need for closure on cases and fear about making mistakes

7. Background: Motivating factors and bias in the collection and processing of forensic evidence
Problems with finger print analysis Studies have demonstrated a lack of consistency in finger print analysis Dror et al. (2011) found that individual finger print examiners differed both from one another (inter observer consistency) and from themselves over time (intra observer consistency)

8. Background: Motivating factors and bias in the collection and processing of forensic evidence
Why does this happen? Attention – Comparing fingerprints is an information processing task and involves attention and visual searching (think of Moray and Simons & Chabris = Our attention can be drawn to something or irrelevant information could distract them – these could be important in finger print analysis) Confirmation bias – This occurs when people observe more, give extra emphasis to or intentionally look for evidence to validate their current beliefs. This bias makes people likely to excuse or completely ignore evidence that would contradict their beliefs

9. Background: Motivating factors and bias in the collection and processing of forensic evidence
Why does this happen?
Observer or expectancy bias – This is when the analysts anticipates the outcome as a result of information from the initial observer (for example, if an officer informs the expert that the suspect has already been identified by an eye witness and the finger print analysis is just needed to confirm their identity)
Conformity effect – This is when a fingerprint expert is asked to validate the decision of a peer, or of a superior, this effect may unconsciously bias them to agree with the original decision if they are aware of it.

10. Background: Motivating factors and bias in the collection and processing of forensic evidence
Why does this happen? Need determination perception - This bias arises from a strong desire to solve a particular crime (for example, this could explain why errors were made in the analysis of the Madrid bomber’s print, as the motivation to identify the terrorist was extremely high) Overconfidence bias - This is when experts may experience overconfidence bias and this may make them believe that they are always right, even in the face of contradictory evidence. The more experienced and intelligent they are, the easier it is for them to defend their biases and beliefs.

11. Background: Motivating factors and bias in the collection and processing of forensic evidence
Why does this happen? Emotional context: The context of the crime influences the analysts decision making process Dror et al. (2005) found when individuals were told the crime was of high emotional context (eg. murderer), this made individuals feel pressure to find a match Other factors such as; the nature of the crime, seriousness of the crime, characteristics of the victim, personal bias of the expert, age of victim and use of weapon

12. Is the analysis of fingerprints… Reliable? Valid?