Over-egging competency
Whilst this case is a useful reminder as to the importance how presentation of competency needs careful consideration there is, though, a vast difference between an expert defining exposure to varying independent elements in a science and/or technology that when identified can assist demonstrate knowledge, skill and experience and that of the an expert's exposure to a number of cases given an actual case-name in which an individual has been instructed to advise.
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Judges' decision in Peterson case puts SBI in tough spot over former agent
Deaver
54, not 500
Michael Peterson was convicted of the murder of Kathleen Peterson, a Nortel Networks executive who was found dead at the bottom of a bloodstained staircase in their Forest Hills mansion in 2001. Jurors have said Deaver's testimony was crucial to their deliberations and verdict.
At the 2003 trial, Hudson allowed Deaver to testify as an expert witness in bloodstain pattern analysis. Regular witnesses testify about facts. Expert witnesses can give opinions, and Deaver testified about his experiments
and analysis of bloodstains in the staircase and on Peterson's clothes. His opinion Michael Peterson murdered his wife on the staircase.
To support his expert qualifications, Deaver testified that he had worked on 500 bloodstain pattern analysis cases, had written reports in 200 cases and testified in 60.
The SBI searched its records and found 54 bloodstain cases that Deaver worked on.
Deaver testified that before the Peterson case he had worked on 15 cases where a fall allegedly occurred. SBI records contained none, according to Ron Guerette, a private investigator who reviewed all of Deaver's bloodstain cases for Peterson's legal team.
Deaver testified that his methodology and experiments were consistent with other experts. At the recent hearing, three national experts said Deaver's work in the Peterson case was unscientific and unacceptable.
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Hi Trew,
This happens in the UK too.
I remember a forensic analyst claiming he had worked on more than 2000 cases, which when scrutinised went down to 20 or so.
There is also the issue of what counts as having 'worked' on a case. Someone who quickly reviewed a statement or a report, or who worked on one small exhibit could say they have worked on the case.
That's very different than being the sole or principle analyst who did all the major work, made all the big decisions and produced the reports for production in court.
There are often differing opinions amongst examiners. That 'is it possible' arguement of the defence is frequently not based on evidence from the exhibits but is based on possible supposition. One way of answering this question is to say "yes it is possible but there are no artefacts to support that arguement". To which the response is often, "so it is possible?".
When it comes to opposing opinions and supposition the barristers might seek to play off one analyst against the other, with the most experienced and most qualified coming out the winner, irrespecitive of whether they are right or not.
I wonder if ISO 17025 has considered labs keeping records of what types of cases their analysts have worked on, whether they were the sole or principle analyst and on what kinds of cases they have worked. This would be quite sensible, whereas some of ISO 17025 looks a little extraneous.
Food for thought.
Steve
steve862, I take your point about ISO17025.
I think it really comes down to what a person means when they state 'cases' with respect to their experience.