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The expert witness in court
 

The expert witness in court

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Slides from the presentation given by Dr Niamh Nic Daéid at the 2010 conference: Moving forward: Legal education in Scotland.

Slides from the presentation given by Dr Niamh Nic Daéid at the 2010 conference: Moving forward: Legal education in Scotland.

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    The expert witness in court The expert witness in court Document Transcript

    • The expert witness in court Dr Niamh Nic Daéid Reader in Forensic Science, Centre for Forensic Science, University of Strathclyde Some key questionsExpertise .. What is it and how is it defined in a legal context ?How is expertise used in court ?How are expert opinions formed/evaluated and what effects this ?How are expert opinions best communicated ? 1
    • Criminal Procedure RulesLord Justice Auld , 2005“Expert evidence may take the form of opinion on factsestablished by the expert or others, admissible by reason ofhis/her extensive knowledge and/or experience.” Or This raises some fundamental Issues for scientific experts“…the expertness of his/her evidence may be essentially and for some evidence types.factual derived from his/her technical knowledge and ability inidentifying the subject matter or as a result of careful analysisand/or observation.” It is particularly problematic for evidence involving an expression of theAn expert must help thelikelihoodby an event or other statistical court of giving objective, unbiasedopinion of matters within their expertise. interpretations which are common in scienceExpertise Evidence given IN COURT by 4 different experts in facial comparison from different backgrounds ‘Stockwell’ revisited: the unhappy state of facial mapping A.Campbell-Tiech and A.Byrnes, Archibold News, Issue 6, June 24, 2005 With thanks to Ian Evett 2
    • Superimposition is dangerous and misleading Superimposition is a good technique Morphological examination can only be undertaken by an expert with medical training Morphological examination does not require any particular medical knowledge Morphological examination is the only reliable Morphological examination is hopelessly subjective technique It has no scientific basis Image enhancement is Image enhancement is indispensable Misleading and dangerousExpertise … not straight forwardHow can this happen ?Is this ‘junk science’ ? If it is, why is it allowed in court ?If it isn’t, why are the opinions of the experts so at odds with eachother ?Who makes the choice about admissibility and expertise ? 3
    • Assessment of evidential value Hypothesis testing Mathematical Databases systems ProbabilisticStatistics reasoning Assessment of evidential value Source Sub source Activity Offence Hypothesis testing Mathematical Databases systems ProbabilisticStatistics reasoning 4
    • Evaluation of scientific information Either: the defendant left the crime stain MATCH Or: some unknown person left the crime stain What is the probability that the crime profile would match the defendant if he had left it? What is the probability that the crime profile would match the defendant if some unknown person had left it? Statisticians agree P(E|Hp) that this is correctly termed P(E|Hd) a match probabilityP(E|Hp)P(E|Hd) Relevance of evidence Transfer of evidence onto receptor LR Frequency of evidence Persistence of in the population evidence on receptor Random presence of evidence Recovery of evidence Frequency of evidence given other scenarios of activity 5
    • Observations BALANCE LOGIC TRANSPARENCY ROBUSTNESS Issues the Jury must consider With thanks to Ian Evett Crime scene stain BALANCE LOGIC MATCHA man is assaulted in the car park of a pub observationA suspect is observed at the scene suspectHis jacket is bloodstainedEvidence of the suspects involvement in the assault is required I have observed the blood staining on the suspects jacket. The evidence is consistent with the blood having come from the suspect The evidence is entirely consistent with the suspects involvement with the assault With thanks to Ian Evett 6
    • Crime scene stain BALANCE LOGIC MATCH observation suspectIn evidence, the suspect says that he saw the fight and gavefirst aid to the victim and this is why there was blood on his jacket. I have observed the blood staining on the suspects jacket. The evidence is consistent with the blood having come from the suspect The evidence is entirely consistent with the suspects involvement with the assault Errrr…. It’s consistent with that explanation as well !!! With thanks to Ian EvettROBUSTNESS The prosecutor’ fallacy The probability of finding that profile if the crime stain had come from someone else is 1 in a billion So it follows that there is a 1 in a billion probability that the crime stain had come from someone else... Hence it is almost certain that the crime stain came from the defendant The second statement does not follow from the first This mistake was made in the Deen, Doheny and G. Adams trials With thanks to Ian Evett 7
    • ROBUSTNESS “…the chance of 2 children dying naturally in these circumstances is very long odds indeed: 1 in 73 million” The chance of 2 children being murdered in these circumstances is also very small… and not articulated in court The statistic was shown to be unreliable in appealWith thanks to Ian Evett R v. Sally Clarke, Court of appeal , Oct 2000 TRANSPARENCY …professor xxxxx accepted that he could not totally exclude the possibility that the hemorrhages were consistent with death by asphyxia He stated that “they are consistent with that because I believe they might be there anyway” What does this mean ??!!?? Can you understand it ??!!! What would this convey to a jury ???With thanks to Ian Evett R v. Sally Clarke, Court of appeal , Oct 2000 8
    • TRANSPARENCY Why should the jury believe you ? ...because of my vast experience in this field ...because I have done a thousand cases like this one ...because I have attempted to place before the court all of the data and literature that may assist the jury. I can show the court where my opinion has been tested under controlled conditionsWith thanks to Ian Evett The evolution of scientific reasoning in forensic science. Observations BALANCE LOGIC TRANSPARENCY Logical framework ROBUSTNESS Issues the Jury Databases must consider Literature and pool of knowledge Reasoned opinion given opposing propositions 9
    • Expert opinion Observations Juror’s common sense Expert opinion Judicial guidance Juror’s appreciation of the expert opinion Issues the Jury must consider Science v ExperienceCritical cases: Science v TechnologyDavies v Edinburgh magistratesR v AdamsR v DeenR v DohenyR v Reed and ReedR v Weller Controlling the paceRvT Controlling biasDaubert CommunicationFrye Disclosure 10
    • Key issuesDo Legal practitioners need to know about science ortechnology ?How do we deal with bias and the suggestion of bias ?How do we understand the subtitles of communication ofscience in the courtsData without rigorous underpinning of published scientificresearch .. Developing legal confusion on this point Thank you ! Dr Niamh Nic Daéid PhD,BSc,BA,FFSSoc,FICI,FHEA,FRSS,MRSC n.nicdaeid@strath.ac.uk 11