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Senn at Presidential Committee

Once again Dr David Senn, who reminds us that he is not in the ABFO leadership and yet he is always popping up representing and advocating for bitemarks, is defending bitemarks in a curious twist that presents the evidence as a major source of securing innocence?

First at NAS, then at NACDL, then at TSFC and recently a stunningly soporific interview on NPR just a few days ago Dr Senn’s views vary from being a sceptic at NAS, through to TSFC where he was far more robust in his defence.

Here is a video of him at yesterdays Presidential Advisory Committee on Science.  I have edited this only to remove the speakers on other topics – including city design, and so you don’t have to sit through several hours, this video is around 18 minutes.

Dr Senn begins in his usual way with a few attacks – not least on the Bush’s (again!).  Let’s be clear on this – he always undermines them, and their work, by stating that they have never done a bitemark and so cant be listened to on the topic.

Imagine this scenario – I believe that a surgical technique kills people, there are data to support my view and I have undertaken animal studies that also support it.  Should I not be listened to because I refuse to undertake that procedure knowing it will do harm?  Of course not, its an idiotic statement, but these quasi personal attacks are not uncommon – either by Dr Senn or indeed others (See the NY DA’s recent memo after they had to withdraw bitemark evidence from a case – a real instance of poor losers but vitriolic doesn’t begin to cover it)

Whats amusing is that Dr Senn attacks the Bush’s scientific methodology  for using an inappropriate means of creating a bite – using a vise grip rather than an articulator. For those of you who listened to the TFSC full committee hearing there was an exchange between Dr. Adam Freeman and Dr. Senn where it became painfully apparent that Senn doesn’t know his articulator from his elbow.  Surely this should undermine all he does?  Of course not, head down and off he goes with further criticism of others without reflecting on his own issues.

Senn lectures TFSC on why the Bushs work is flawed by pointing out the vise grip - later he stumbles on his own lack of knowledge of articulators
Senn lectures TFSC on why the Bushs work is flawed by pointing out the vise grip – later he stumbles on his own lack of knowledge of articulators

Senn denies that any error rates are known – of course there are – the work of Whittaker in the 1970s would be one example and there are others.  Does he just not know the literature or is he being misleading?  My sense is that we would say that there were errors in the methodology and the science isn’t good enough etc etc.  It does beg the question why doesn’t he undertake the necessary research?  When asked this he always states that he is not an academic?  However he does undertake research and has published it in the past.

Senn never declares his conflict of interest – this goes beyond his ABFO membership into the fact that he is employed by a University to teach bitemarks!  When, as surely they will be, bitemarks are either eradicated or restricted and no one wants to take his course what will happen?  Of course he will argue that there is lots to forensic dentistry beyond bitemarks, and he would be right – but this would be a major blow.

What is interesting here is that he also concedes that at his 2009 NAS hearing, he only covered the weaknesses of bitemarks – not the strengths.  We know this to be true from not only the available presentation but also his NADCL lecture.  He has recently sought to distance himself from the NAS report saying they didn’t do a good job and has been highly critical of them – however, they were led by the experts that present to them – and in the case of bitemarks there was only one – Dr Senn.

Have a look at the video – within moments the Judges are at fault and that the committee may not understand the rules of evidence. He claims that educating judges will help but does not explain how this helps BM evidence.  He then does not address any of the questions that were given to the ABFO to answer (see below).  Unlike the other speakers who all addressed these in detail he simply sidesteps this and instead Senn presents bitemarks on children in an emotive attempt to impress the committee.  No mention of science, no mention of skills and a simple show and tell on bitemarks.  He even presents a case that is not his and then cannot answer questions on it.

Unbelievably he states that the defence bar would object to BMs being thrown out of Court – I think rather unlikely and he avoided any mention of the wrongful convictions that have been associated with BM evidence.

As with the TFSC he wasted an opportunity to show the science, engage with the process and make some real sense of what needs to be done to ensure that BM evidence has a robust scientific basis.  Instead he ignored the questions, ignored the process and just filled the time with irrelevance.  The honest answer is he doesn’t know the science, and if he does he wouldn’t be prepared to share it as he knows it undermines his position.

Questions posed to Senn and the ABFO:

Q1:  What studies have been published in the past 5 years that support the foundational aspects of each of the pattern-based forensic science methods, including (but not limited to) latent print analysis; firearms/toolmarks; shoe/tire prints; bitemark analysis; questioned documents? What studies are needed to demonstrate the reliability and validity of these methods?

Q2:  Have studies been conducted to establish baseline frequencies of characteristics or features used in these pattern-based matching techniques? If not, how might such studies be conducted? What publicly accessible databases exist that could support such studies? What closed databases exist? Where such databases exist, how are they controlled and curated? If studies have not been conducted, what conclusions can and cannot be stated about the relationship between the crime scene evidence and a known suspect or tool (e.g., firearm)?  

Q3: How is performance testing (testing designed to determine the frequency with which individual examiners obtain correct answers) currently used in forensic laboratories? Are performance tests conducted in a blind manner? How could well-designed performance testing be used more systematically for the above pattern-based techniques to establish baseline error rates for individual examiners? What are the opportunities and challenges for developing and employing blind performance testing? What studies have been published in this area?  

Q4: What are the most promising new scientific techniques that are currently under development or could be developed in the next decade that would be most useful for forensic applications? Examples could include hair analysis by mass spectrometry, advances in digital forensics, and phenotypic DNA profiling.  

Q5: What standards of validity and reliability should new forensic methods be required to meet before they are introduced in court?

Q6: Are there scientific and technology disciplines other than the traditional forensic science disciplines that could usefully contribute to and/or enhance the scientific, technical and/or societal aspects of forensic science? What mechanisms could be employed to encourage further collaboration between these disciplines and the forensic science community?

Q7: Please share any additional comments.





About Iain Pretty

Iain Pretty

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