"Don't throw the baby out with the bitemark!"  

--Dr. Janice Klim-Lemann 

   It seems to me that in the debate over bitemark analysis, folks have spent way too much time arguing about the uniqueness of the human dentition...a topic I did a presentation on at the American Academy of Forensic Sciences meeting in 2008.  I believe the issue of whether everyone in the world has a unique set of teeth or not is one that likely cannot be scientifically proven.  I also think the issue is a red herring that does not actually go to the heart of the problem.

   The germane question is, I reckon: do each of the suspects in a case have a 'unique enough' set of teeth that I can distinguish between them in a bitemark made on human skin?  I don't really care if one of the suspects has a dental doppelganger on the other side of the world who could not have possibly been involved in the case--that's irrelevant and immaterial to the case at hand. 

   What I do care about is this: among our suspects, does each have teeth that are distinctive enough from the other suspects?  Now, we're going to have, of course, a lively discussion about what 'distinctive enough' means, but at some point in these proceedings some common sense has to be injected.

   So, what is Fig. 1 a photo of?

 Fig. 1.

   I claim this is an image of a tire track in snow. Do I really have to explain how I came to that conclusion? Would anyone really dispute this is a tire track?  This one was made in Texas, but folks up north see these all the time.

And, now, what is Fig. 2 a photo of?

 Fig. 2.

    I allege this is also an image of a tire track in snow. Again, do I have to explain how I know this is a tire track?  And I further claim a different tire made this impression than the one in Fig. 1 above.  How do I know?...well, I can see it. They don't "match." That's not a difficult thing to see.  There's not really a scientific basis for my conlcusion or a scientific method required here--I can simply see the difference.  Again, at some point common sense has to prevail.  It's pattern-matching, not rocket surgery.

   Yet one more...

 Fig. 3.

   And I also claim this tire track in Fig. 3 is from a different tire than the above in Figs. 1 and 2.

   I drive a car that happens to have "high performance" tires on it. I also have an SUV that has "general utility" tires, and the tread patterns on the sets of tires are very different from each other. On the day I took these photos, my wife had driven our SUV down the street (Fig. 1) and I had driven my car down our street, as well (Fig. 2). A foreman from a construction crew building a house nearby also drove his pick-up truck with "off road" tires down the street that day--I claim we have here a closed population (some now call this a "defined population").  Those were the only three vehicles on our street that entire day--we live in a small, gated community, and the traffic through the gates is very limited and videotaped.  Now lets say, hypothetically, that one of these three vehicles apparently slid off the road during the snowstorm, knocked down a streetlamp, and then left the scene.  Assume for this hypothetical example the tire tracks shown in Fig. 3 led directly to the streetlamp, and then led away from the scene through the exit gate of the neighborhood.  The folks from the homeowners' association want to know who's responsible for the damage so the culprit can pay for repairs (unfortunately, the recorded video is only of the gates, and not of all the streets).

   Now, we can back my car out of the garage, drive it through some fresh snow (or other appropriate tire impression material), and document the tread pattern made by my tires.  And then do the same thing with my SUV.  My vehicles can readily be excluded as a "match" to the pattern in Fig. 3. Do we really need a scientific explanation for that?  NO!!--we can simply and clearly observe the difference.  Exclusion can be a very powerful result and extremely important to those folks who are excluded. 

   If we can track down the truck in the videotape and get a photo or some kind of impression of the tires, maybe we can match the truck tires to the tire tracks at the hypothetical scene.  Exactly how that would be done and the actual comparison would be up to the trained crime lab tire-tread analysts who do that sort of thing for a living as I certainly do not claim to be an expert in tire track analysis (or in any other non-dental area, such as fingerprint analysis), but you get the idea.  The trained experts might be able to do an inclusion, but its really not that difficult to do an exclusion.  Why?...well, again, we can see my tire tracks don't "match" Fig. 3.  Do I really have to provide an elaborate scientifically-based explanation as to why I think the patterns are all different?  Look at them!  Clearly, they are not the same.  They don't match.  Several courts have held that, similarly, jurors are perfectly capable of looking at bitemark evidence and weighing its credibility. 

   And, to bring in another dental example, what is the scientific basis for a dental ID comparison using ante- and postmortem radiographs?  One might just as well claim there's not much of such a basis there, either.  We do this procedure all the time, no one questions it, and dental ID's are not litigated much at all.

   The issues in bitemark analysis and comparison are not very different from the above tires-in-the-snow scenario.  But the rub is that, in bitemark analysis and comparison, there have been challenges in court by non-board-certified, amateur odontologists and, even--non-dentists!--that the discipline does not have a scientific basis. Really?  In what literature space have these "experts" been searching?  There are the very well-developed fields of perceptual psychology, machine vision, facial recognition software, and 2D and 3D pattern matching in engineering and biology, just to mention a few areas, that have addressed the very same analysis and matching issues found in bitemark comparison.  There have even been cases where the defense experts themselves have attempted to discredit bitemark analysis by (mis-)applying some of these very same scientific principles, such as 2D Procrustes analysis, and then turn around and claim there is no scientific basis to the discipline.  Although the scientific methods the self-appointed experts used are not generally accepted in the odontology field, they nonetheless cannot use scientific methods to bolster their position and then rationally claim there are no scientific methods to be found.  It does not compute.

  And, by the way, (mis-)use of 2D Procrustes analysis by some of the amateur odontologists and biologists is interesting.  My undergraduate training was in biology.  I am in graduate school in a biology program.  I have some understanding of biology.  Now, I reckon 2D Procrustes analysis could be a very powerful tool when being used to exclude a suspect.  Analysis of the shape of the patterned injury, exclusive of considerations of size, could certainly show that someone could not have made a bitemark, I.M.H.O.  The N.A.S. Report itself even acknowledged bitemark analysis could be useful to exclude suspects.  The amateur odongologists and biologists used Procrustes analysis, however, to include dentitions that they claimed "match" each other.  Let's think about that for a moment.  They say real board-certified practicing odontologists can't reliably "match" a dentition to a bitemark (an inclusion), yet, on the other hand, perversly claim they themselves are perfectly capable of "matching up" (an inclusion) models of various folks' dentitions to each other using an unapproved, untested, unvalidated procedure performed by amateurs? Hmmm.

   Again, think about that.  I would say that these "experts" have just "talked themselves out of court," as we say, by precisely providing more than a scintilla of scientific basis to the discipline of bitemark analysis.  "Thanks, guys!  I'm sure you didn't mean to do it, but thanks!!  I certainly don't consider you folks to be experts, but if other organizations are going to rely on you, well, I think you've 'shot youselves in the foot' " (-selves? -self? foot? feet?)

   The amateurs have expressed great admiration for the somewhat controversial N.A.S. Report.  Let them please remember that recommendation #7 of this report strongly urges that only board-certified experts should be allowed to practice in a forensic discipline or testify at trial.  Yet, the non-board-certified self-appointed amateurs want to keep testifying in court and even dismantle the only legitimate certifying organization for forensic odontology?  How is that making progress? 

   (And please remember, I did not write N.A.S. Recommendation #7.  I did not suggest it.  It was written by esteemed scientific minds who thought that was a good idea. [B.t.w., the A.A.F.S. Board of Directors adopted a public position statement endorsing all 13 of the recommendations, including #7.]  Similarly, I did not write the N.A.M.E. [National Association of Medical Examiners] standard for accreditation that requires M.E.'s offices to have an A.B.F.O.-certified odontologist available for consultation.  They thought that was a good idea.  I'm just the messenger, shoot someone else if you don't like the message.)

    I'm not sure why these amateurs keep getting the press coverage that they do.  They are not forensic odontologists.  For hypothetical example, would one turn to a "forensic odontologist" who has never actually done a bitemark case?  ...or who has no formal training in forensic odontology?  ...or who has never challenged a board-exam?  ...or consult an "expert" that is not even a dentist...much less a trained forensic dentist?  ...or someone who has not had any graduate-school-level training?  ...or what about a so called "biologist" who has no training in biology?  ...or someone who was board-certified at one time and practiced in the field for years, but then mysteriously "retired"?  A very pithy question for these sorts of folks might be: "if you are not board-certified in odontology, why are you not?" 

   Of course, I certainly do recognize and admit certification and accreditation don't fix everything, and do not remotely guarantee a specific analysis will be "right."  Further, when we adopt S.O.P.'s (standard operating policies) and standard protocols, and we become board-certified and agree on "accepted" procedures, and we have lab inspections for accreditation according to certain international criteria, those S.O.P.'s and protocols become pretty much fixed in stone.  Those become "THE way" to do an anlysis, and one does not deviate from that, lest s/he risks censure.  This could arguably certainly stifle innovation and research into better, modern methods.  But, in the final analysis, certification and accreditation by a body of peers should count for something, but keep in mind--setting up your own lab and calling it a "forensic research lab" doesn't count for much--not any more than, for example, writing a research paper where nearly all the references are to one's own other publications. And, again, don't forget, I do see myself as a scientist first, and I am all on board with doing more relevant and appropriate research--do not misconstrue that!

   Furthermore, it is, at best, extremely disingenious for defense types to decry the credibility of bitemark evidence in the prosecution's hands while, at the same time in other cases, happily using bitemark evidence, when convenient, to eliminate their clients as suspects or even exonerate convicted clients of crimes.  Bitemark analysis and comparison either works or it doesn't.  Virtually every odontologist I know in the U.S. who does bitemark cases has worked for prosecutors at times and on other cases for defendants at times.  It doesn't matter to us whether we are working for a prosecutor or for a defense attorney--we look at the evidence and render an unbiased opinion. 

   There have been a few recent "high profile" cases where odontologists have assisted attorneys  in post-conviction cases secure exonerations for their clients (see Wilhoit, Krone, Stinson, Kennedy and Brewer, for example).  These were cases where the conviction, at least partly, involved a faulty bitemark analysis and comparison.  These attorneys have unfailingly turned to members of the ABFO to assist in the post-conviction relief, and the ABFO members have unfailingly "stepped up to the plate" and performed admirable service.  Why do the defense attorneys and post-conviction attorneys rely on bitemark analysis and comparison when it can help their clients, but turn around and piously and self-righteously claim bitemark analysis is not credible or reliable when a prosecutor uses it? Well, I happen to be an attorney, too, and I fully realize why they do it.  Doesn't make it right, though!

   Unquestionably, bad bitemark analyses contributed to some of these convictions, and that is unexcusable; I am not an apologist for those bad analyses.  But, looking at the cases, it is seen that the problem has been, not that bitemark analysis is unreliable, but, rather, a faulty analysis was performed by an individual.  The post-conviction folks don't argue that bitemark analysis is incredible and should not have been admitted at trial, they argue along the lines that "the analysis done for the trial was incorrect, and we have two (or three or four) odontologists who have re-anayzed the case with a different conclusion than the original dentist..."

   Why does the defense bar argue that way? Because they know that bitemark analysis is a very powerful tool when used to exclude a defendant as "the biter."  They don't want to lose this tool when it suits their purposes.  Whatever they argue about using bitemarks to include, exclusion of the innocent is something that is profoundly important to those so excluded.  The criminal justice system should not deprive defendants of that defense--seems to me that depriving a defendant of a valid defense is, oh what's the word?...ummm...unconstitutional.

    Here's a link to a more balanced article about the recent bruhaha over pattern-matching disciplines....this is worth looking at:  http://www.science20.com/keeping_the_gate_a_science_and_justice_blog/blog/standards_needed_for_postconviction_review_of_forensic_evidence-154943 

   These issues are, of course, very important to odontologists who are involved in these analyses every day.  We are aware of and have learned from the problems from past cases.  We have taken steps to address and correct the problems.  We do not perform analyses "in a vaccuum."  Research has been done.  Protocols and procedures have been updated.  We have training programs.  We don't now do bitemark analyses like those done back in the "good old days."

   Folks like those on the recently appointed National Commission on Forensic Science must realize at some point that merely repeating the knee-jerk reaction that "more research must be done" is simply not the answer.  "More Research!!" was the recommendation of the N.A.S. Report--what in the world would one expect from the National Academy of Sciences?  Would the N.A.S. recommend more musical training for everyone?  Of course not, they're invested in research as the way to answer all questions--reminds me of the old adage "when the only tool I had was a hammer, every problem looked like a nail."  (And, BTW, if bitemark analysis is such a poster child for bad forensics, why was not even one odontologist appointed to the Commission?  Something's haywire if "they" want to keep beating up on "us," but won't even give "us" representation on the Commission!  Can you say "trial in absentia?"  Or ex parte proceeding?)

   Dentistry, including the forensic variety, is as much an art as it is a science.  There's absolutely nothing wrong with that.  Experience counts in a clinical discipline!!  Don't get me wrong, I think of myself as a scientist first, so go ahead and do all the research you want...but consider this: a few years ago "evidence-based practice" was The Next Big Deal in medicine and dentistry.  Sackett et al. define this as the “conscientious, explicit and judicious use of the current best evidence in making decisions about individual patients.” Right on.

  Essentially this means, evaluate all the current research in the journals and figure out what's the best treatment.  Precisely how to interpret the evidence and how to apply it is of course an open question and open to much subjective interpretation. The A.D.A. even has a webpage devoted to evidence-based practice.  But let me ask this: when did we not consider the most recent research and try to figure out what's the best treatment for a patient?  We've always done that!  In all honesty, has the concept of "evidence-based practice" made much of a difference in the practice of medicine or dentistry?  No, not much.  Not much at all.  And just doing more research is not the final answer.  Why does this approach not work well?  Because it is very easy to standardize protocols and procedures, but it is impossible to standardize patients.  The analogy to forensics should be obvious.

   You want to know why there are no on-line dental schools or medical schools (or even no accredited on-line law schools)?  Because you can try to teach all the science or law you want on-line, but you can't teach the art of how to apply that science or  how to practice law on-line.  You have to be mentored in person by folks who have much experience.

   Consider: back in the day, if, gods forbid, I needed heart surgery, where would I have gone?  To Houston, of course, and I would have tried to become a patient of either Dr. Michael DeBakey or Dr. Denton Cooley.  Why?  Well, while their Resident surgeons-in-training know all the science there is to know about heart surgery, they haven't done many procedures on actual patients.  I would want one of the top surgeons who has personally done a zillion procedures to operate on me.  Why?  Experience.  Try to quantitate that.  One can know all the science there is to be had about a discipline, but precisely how that science is to be applied in a specific case is the crux of the issue, and that is learned only by experience.

  And it is precisely the same in the field of bitemark analysis.  Back in "the good old days," forensic odontologists were self-taught (just like the amateurs who are now critiquing the field are self-taught and self-appointed experts).  There were no standardized protocols or procedures "back in the day."  There was no formal training avaiable.  They worked alone. Organizations and publications devoted to forensic odontology were few and far between.  Again, yes, they did some "bad" bitemark cases back then, no question.  And, again, we do not make excuses for the bad analysts.  Those cases are inexcusable.  BUT--we have learned a great deal from the mistakes made by our predecessors.  We have taken many, many, many steps to correct the errant ways.  And face it, some people are simply just better at bitemark anaysis than others.  But, bottom line, we have learned and evolved from experience, just as other any field evolves, and we have moved forward.

   And, to conclude, remember when we go into court we are rendering a doctor's opinion.  That may be based on science.  That may be based on experience.  May be a combination of the two.  And that expert opinion we give is a far cry from merely repeating a readout from some automated piece of lab equipment such as an "intoxilyzer" or H.P.L.C.  What we do in bitemark analysis requires reasoned interpretation.  It requires experience.  It is an art.  You want to argue it's not a science?  Fine...ok, so what?  That doesn't make the analysis invalid.  That just makes it harder for the other side to argue with...after all, an opinion is an opinion is an opinion.  I do not go into court and offer my opinion as a statement of scientific fact.  The jury decides what the facts are, not the expert.  I offer my opinion as an opinion--it's what I think--and that may be based on a number of factors.  Certainly, an opposing expert may have a different opinion, and one's opinion may arguably be incorrect in a specific case.  But, once again, we're not saying we're stating an indisputable fact.  We're rendering an opinion. It doesn't have to have a scientific basis--PLEASE show me any definition of "evidence" where any source says evidence must be scientific, if you can.  You can't.  Bitemark analysis is still a technical discipline...at the very least, it is other specialized knowledge.  As we say, it goes to the weight and not the admissibility.  If you don't understand what I'm driving at here, then you really shouldn't be thinking about testifying in a bitemark case.