CSI boffins: You can't ID crims from bitemarks on victims Topflight CSI boffins have cast doubt on the apparently "commonly held belief" in forensics that criminals can be positively identified from the bite marks they leave on their victims. "Bitemark identification is not as reliable as DNA identification," explains the study's lead author, Prof Raymond G Miller of the University …
I do seem to recall a program on the TV quite a few years ago about some criminal who was caught after leaving a bite on someone or something.
An odontologist was asked by the police for help. This clever fellow told the fuzz what the crim would look like, with overhanging upper teeth.
I'm a little bit surprised to read that "Bitemark Evidence: A Color Atlas" is apparently "the only comprehensive textbook on the subject of bitemarks", cos there is a quite a list of books on this specialist subject here: http://www.bafo.org.uk/resources/textbooks.php. One of them shares a suspiciously similar title: "A Colour Atlas of Forensic Dentistry".
It seems forensics has been badly abused by overzealous redneck prosecutors until the DNA era. Some of the worse methods are bitemarks, handwriting, and even eyewitnesses (been proven that humans under stress are terrible at remember details). I guess its a good thing DNA science came along or we would still be lynching even worse the first suspect that takes the heat off the DA.
it's still useful.
If you have an unusual bite (say, it's in a W shape) then you know you're looking for one freaky looking perp. Or at least someone whos dentist would remember.
Same with the diameter of the bite- you can probably cross a load of people based on that alone.
And it's probably useful- with really fine analysis- to help discern between people.
I hate objections like this. If they upheld all of these daft objections then "He had light blonde hair" wouldn't be acceptable as it's not particularly precise. Not being able to catch someone on this one single solitary bit of evidence isn't that bad- it's only part of the puzzle. In fact I'd hate it if "he has good teeth, so did the killer- 'nick him!" was SOP for the police.
Human Bite Marks was the name of the pub grunge-metal band my friend was in back in the 90s. They got quite a few gigs in their time, mainly because of the imagery evoked by the name!
As far as testing on human subjects goes, they could easily use rubberised polymers if they want to get a broad sample for these tests. I've seen some quite realistic skin-like plastics that they could use. No need to actually use humans subjects - if they just thought a bit.
Though I can't say I'd enjoy biting down on a plastic-coated rubber rod myself, but I'd do it if they paid me enough...
I actually am an Odontologist who routinely undertakes bite-analysis cases.
The paper referred to is correct in one sense - if you were looking at a large population you may find a number of individuals with broadly similar tooth positions and jaw shapes which could produce similar bitemarks.
HOWEVER, in every case I have investigated I have been presented with a small number of suspects, all of whom are suspects due to other evidence.
One is not therefore looking at the bite against the whole population of, say, a city, but against just the members of a family / workers in a nursery / attendees at a party / etc.
It would be dangerous and irresponsible to proceed with a trial based solely on one piece of evidence, which is why (in the UK at least) we do not, but the paper does not clarify the fact that cases would not realistically be tried on the basis of just a bitemark. Rather, it attempts to debunk the method in the court of public opinion.
And what of bite marks of (other) animals? Knowing whether it was a wolf or bear that munching on the unsuspecting hiker would be very useful... especially if it turned out to be the domestic terror(ier) owned by the idiots down the street...
PH, because I would love to study her orthodontal impressions. :)
It was a US university which performed the study. In the US, they only have 3 different molds for your teeth. Everyone between the age of 13 and 18 have their teeth twisted, contorted, and replaced if necessary, to fit one of these 3 molds. So what they are saying is the US's obsession with fixing their teeth has made it impossible to tell one persons teeth apart from another (unless the bite came from a pre-pubescent child). What a suprise!!
I've watched CSI on TV - you just need to go into the glass, chrome and moody lighting lab, scan the teeth and bite, and wave your hands around in front of a 3D computer monitor a bit until the computer flashes up 'Match Found' with the driving license photo of the 'perp' in a funky typeface.
that's the problem with this proclamation, it seems to just give credence to DNA, a bite mark will often contain some DNA.
"With DNA, the probability of an individual not matching another can be calculated", well anything is calculable whether or not the result or the evidence for the calculation is compelling or not is the real issue.
And if someone is going to say something like that, I want to see the working.
DNA can be abused just like anything else, to convict overwhelming evidence is needed, better to let free 6 billion guilty, than put one innocent in jail.
@Adam Foxton
'In fact I'd hate it if "he has good teeth, so did the killer- 'nick him!" was SOP for the police.'
Of course this isn't the way our fabulous boy [and girls] in blue work. They say "The victim's been bitten to death, our suspect used to have teeth, good enough for me, your nicked."
@Charles Manning
'Perp was a 6ft white guy doesn't mean you lock up the first 6ft white guy you find.'
Doesn't it?
You _SURE_ about that?
You spell your job title/type with a capital letter? As all of us Teachers, Network Technicians and Computer Scientists do? Nice try.
Bitemark analysis will be good for excluding suspects, but can't help against "It woznt me, it woz another guy that dones it an' ran awayz". Plus it will give you the species of attacker with reasonable certainty.
...that they are a useful tool for the police to narrow down a search or eliminate suspects. However, they are not sufficently strong evidence to convict someone in court. Presumably, once teh police have used the bitmark analysis to help them find a perp, there will be other evidence that they can then use to convict.
> "In the US, they only have 3 different molds for your teeth."
"What does that even mean?"
Seen Simon Cowell's teeth? That's mould number 3.
Just have a look at the teeth of hollywood celebs. Each one has perfect teeth. They're probably identical to the person next to them as well...
Mr Odontologist, how come you missed two vital pieces of information in your description of the use of forensic bite-analysis?
1. There are no double blind studies as far as I can find to show that this is an evidence based, scientific technology rather than just you and your colleagues’ opinions (after a big night out... perhaps).
2. Even if matches were shown to be within acceptable rates of error, it would still be useful only for eliminating suspects, not convicting them. (Say the right incisor imprint is missing and the suspect chews with a good set of 32. Shucks!)
The idea that you can identify a person from a bite mark is probably just as ludicrous as it sounds (with the above given exceptions). This probably explains the lack of double blind, statistically significant studies! No pseudo science ever has them.
I guess at this late stage nothing about “forensic science” surprises me. Whenever my brother and I, (with a collective 70 years of scientific research and technology between us), feel like a good laugh we just look up the latest forensic "science" pratfall. Better than the Three Stooges!
This reminds me of The Wire - season 5. The "homeless serial murderer" which McNulty embellished further by creating bite marks on the victim. The FBI made a good point though, there was no trace of saliva so they concluded that the biting was staged... my point here - unless you're acting like McNulty and using fake dentures to do the biting, isn't the biter always going to leave at least a bit of saliva and therefore traces of DNA?
So perhaps the moral of the story is, if you get bitten, wait until you have a swab test taken before you wash and clean the skin.
Firstly, thanks for (some) well-considered, constructive observations.
As a profession, we are well aware of the lack of quality research into bitemarks, most importantly the use of a gold-standard that is acceptable both in terms of diagnostic research and is also forensically relevant, but several studies are currently under way to address this as far as possible.
One current PhD thesis is analysing the prevalence of individual dental features (rotated incisors, etc) within the population as a whole and is producing very useful data, but this is unlikely to yield useable results for another 2 years. Other studies have shown that the biting surfaces of the teeth do appear to produce a pattern unique to an individual, but these are based on analysis of models of teeth rather than bitemarks, and typically have involved smaller sample sizes (<100).
The problem in relating the teeth to the mark lies in the fact that a bite is, by its very nature, dynamic. The teeth and jaws move in the action of biting, the biter and victim move relative to one another (unless the victim is restrained or unconscious), the shape of the bitten tissue alters depending on compression from the bite itself, muscle movement below the skin and the presence of the skeleton relative to the skin surface. These can all produce distortion within the injury, and we are trained to assess this in tandem with the physical evidence and statements provided in order to pick up on any discrepancies. Exclusion is a big part of the process.
As far as research goes, we are unfortunately limited by ethical regulations - it's bloody difficult to gain approval to conduct bite tests just on cadaveric animal tissue, and live-subject research is an absolute no-no!
Even where studies have been conducted on cadaveric tissue, the data cannot necessarily be directly translated to the response of living tissue, as tissue reactions, healing, etc all impact on the appearance over time.
We accept the limitations of the analysis and comparison, and do not examine cases in a frivolous manner. Our duty in such cases is not to convict - it is to provide impartial, unbiased expert opinion to the court (at least, that is how we do it in the UK). I have seen plenty of cases where there is insufficient evidence to even support the allegation of a bite, never mind a comparison with a suspect, and have no qualms about stating such in my reports.
The defence always have the opportunity to call their own expert to assess the case, which helps keep everyone up to date with current research and provides scope for an alternative opinion to be presented.
I take no issue with anyone who wishes to query the methodologies or basis for the work we do, it is welcomed as it maintains an impetus for research and improvement. Suggestions for conducting high-standard research will be welcomed gladly, as few of us are based in academia and thus have little scope to undertake research for ourselves. We are heavily reliant on our research colleagues in that regard.
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