Bias and expert witnesses

• What is an expert witness?

  An expert in one or more fields
• Why does the court need an expert witness?

  To explain issues outside of their knowledge
• Who can be an expert witness?

  Scientists, engineers, medics, and others
• What is expected of an expert witness according to criminal procedure rules part 19?

  To be objective and unbiased
• What should an expert witness communicate to the court?

  Complex scientific issues in layman's terms
• What should a forensic scientist NOT give an opinion on?

  The probability of guilt
• What is the purpose of the forensic scientist's statement?

  To declare their duty to the court
• What is the overriding objective of an expert witness?

  To help the court achieve justice
• What is the framework used by forensic scientists for case assessment?

  Case assessment and interpretation (CAI)
• What are propositions in forensic science?

  Statements used to work with hypotheses
• What are the different levels of propositions in a burglary case?

  Source, activity, and offence
• What can forensic scientists deal with?

  Source and activity
• When is a forensic scientist typically instructed by the prosecution?

  Early in the case
• What is the general case progression for the prosecution?

  Information, scene visit, assessment, report
• What is key to everything the expert does?

  Communication
• What are contemporaneous notes?

  Notes made at the time of an event
• Why are contemporaneous notes important?

  They provide an accurate report of actions
• What should be included in contemporaneous notes?

  Key details like case number and writer
• What is a short format statement (SFR)?

  A brief summary of findings and conclusion
• What is the purpose of a full statement?

  To provide full examination and conclusions
• What is unique about the expert witness in court?

  They provide evidence of opinion
• What should an expert do on the day of the trial?

  Report to a court official upon arrival
• What happens if an expert makes a serious error in court?

  Their opinion could be deemed worthless
• What is bias defined as?

  A skew that predisposes a process
• What is cognitive bias?

  Mental shortcuts affecting judgment
• What is confirmation bias?

  Looking for evidence that supports a hypothesis
• What is expectation bias also known as?

  Experimenter's bias
• What is the role of a lead scientist in a case?

  To manage the case and set examination strategy
• How can cognitive bias be minimized?

  Through training and contemporaneous notes
• What are the types of cognitive bias?

  • Anchoring effects
  • Confirmation bias
  • Contextual bias
  • Expectation bias
  • Reconstructive effects
  • Role effects
• What is the case example of cognitive bias in forensic science?

  • Madrid bombings (2006)
  • Brandon Mayfield identified by FBI
  • Based on 10 matching features
  • Important differences overlooked
  • Eventually excluded by Spanish Police
• What are the steps to minimize cognitive bias in forensic science?

  • Cognitive bias awareness training
  • Keep contemporaneous notes
  • Follow external guidance
  • Consider both prosecution and defense propositions
  • Blind checking of work