Home / ABFO Diplomates / 1 in a million bitemark case looks to fail – another wrongful conviction overturned?

1 in a million bitemark case looks to fail – another wrongful conviction overturned?

Steven Mark Chaney was convicted in 1989 of murdering John Sweek – he has been in prison ever since.  Key to his conviction was forensic dental evidence supplied by two odontologists – Jim Hales and Homer Campbell (now deceased).

Both men spent hours on analysing an injury to Sweeks that they stated was a bitemark and ultimately linked it to the dentition of Chaney.  But Hales did not stop there – he went on to claim that the linkage, or certainty between the dental study models and the injury was “1 to a million (sic)” This application of medical statistics is more familiar to those reading the transcripts of testifying DNA experts, not odontologists.

There is not any mathematical evidence to support this – not then, and not now. But it was key to securing the conviction with one juror later saying that it was the bitemark evidence that convinced her of Chaney’s guilt above all else.

Hales, to his credit, has sought to distance himself from his statements – very much like Karazolous in the recent Pittsburgh case. Hales stated that:

Conclusions that a particular individual is the biter and their dentition is a match when you are dealing with an open population are now understood to be scientifically unsound

Here he refers to the change in bitemark guidelines published by the ABFO in 2013 – where the use of open and closed populations was raised as a means by which forensic dentists should assess the scope of their conclusions. The ABFGO make much of this change claiming that it presents clear intent by the organisation to refine, and revised its guidelines based on scientific evidence.  Its not clear what the scientific finding was that changed their views – perhaps it was the increasing number of wrongful convictions?

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Trial testimony – this figure does not appear in any literature and Hales couldn’t identify it

Chaney’s case was taken up by the New York Innocence Project and, using the 2013 Texas legislation on scientific advancement, they state that he should be granted relief.  In addition to the clearly erroneous bitemark evidence there  was also evidence presented of prosecutorial misconduct in relation eye witnesses and also blood evidence.

If you look in the Journal of Forensic Science – you will never find a paper or study that confirms these numbers and the ABFO have never undertaken a study that reports the kind of data referred to here.  The only possible thing could be the ABFO’s attempt at a scoring system (devised in 1984 following the fist bitemark committee meeting in 1981, published in 1986) it was later discredited and removed from use by the ABFO in a letter to the editor of the JFS.

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Chaney’s case will be heard later today (Monday 12th October) in Dallas – the prosecution is expected to respond at that time.

Further reporting on this story at:





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About Odont1

Odont1 is a seasoned forensic dentist, researcher and educator with an interest in progressing the science of the discipline while retaining those elements that are evidence based and useful to the judicial system at any level.

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