Texas to Execute Humberto Leal, Conviction Supported by Unreliable and Unsupported Bitemark Opinion

By Dr. C. Michael Bowers

The impending July 7, 2011 execution of Mexican national Humberto Leal ( has the US State Department and the Mexican government hopping mad at Texas. A last minute “Hail Mary” petition to the US Supreme Court and a State of Texas appellate court requesting “timely” DNA testing of evidence available since 1995 has so far fallen on deaf ears in that fair state. Leal was convicted in 1995 of murder and rape of a 16 year old female. His sentence of death was contingent on the aggravating circumstances of the rape. What has been ignored by the Texas prosecutors and the Texas judiciary since 1995 is the DNA from the victim’s body and underwear have never been tested. Possibly the report and testimony of the prosecution’s forensic dentist helped as a substitute for later DNA testing. Dr. Alder’s (of the U of Texas San Antonio forensic dentistry department) report stated, in his conclusion…

The bitemarks on ME #94-0770 are consistent with the dentition of Humberto Leal and therefore were inflicted by him.”

The term “consistency” may sound powerful to the layman, but in a forensic sense, it is meaningless due to its silence about chances of someone else’s teeth being making the same marks. The ABFO standards do not equate “Are consistent” to a positive match (i.e.“ therefore were inflicted by him”). Moreover, Dr. Alder provides no analytical nexus to connect the two conclusions in this statement. The only forensically acceptable means of making a positive identification of a biter is through the use of DNA obtained from swabbing the injury for saliva.

In fact, it is now widely recognized that bitemark analysis – when used to make “positive” matches – masquerades as a reliable scientific discipline. In the Leal case, there is no scientific connection between the observational opinion of “consistent” and the claim that “the bitemarks were therefore inflicted by him.”

Dr. Alder’s forensic dental report only gets worse, as he did notice “inconsistencies” between the bitemark and Mr. Leal’s teeth. This should result in a “mis-match” or exclusion of the defendant as the biter. But wait, Dr. Alder has a special talent, bitemark attack reconstruction. He was not present during the attack, yet felt competent to recreate a scenario in his mind and, in doing so, devalued his observation of patent inconsistencies between the patterns on the victim’s body and his exemplars of Mr. Leal’s teeth. His reports clearly states there were non compatible (i.e. inconsistent) misalignments between the bitemark and Mr. Leal’s teeth. His report continue, “There were numerous points of ….

Individual consistency and no marks which were unexplainably inconsistent with Mr. Leal’s dentition.

Now, how did he discount the documented inconsistencies? He didnt say. He was more attracted to the consistencies. He considers “explainability” of the inconsistencies as proof of his accuracy. It actually has the opposite effect. As mentioned before, Dr. Alder had special abilities and that’s all it takes to make an case for Humberto Leal’s guilt.


Bitemark Certification Board Objects to Defense Subpoena Demanding Release of Expert Opinions

By Dr. Michael Bowers

Recently, in the District of Columbia Superior Court, the forensic organization that certifies bitemark analysis made a failed attempt to suppress expert opinion in a bitemark case. The case in point is US v Ridley, a recently tried murder case involving a human bitemark on the deceased victim. Preceding the trial, there was oral argument over the admissibility of expert reports unfavorable to the District’s prosecution theory of the defendant’s guilt.

The prosecution’s expert, who is an ABFO certified forensic dentist, used the photographs of the victim’s bitemark and the defendant’s dental models as the bitemark testing material for the 2011 ABFO certification exam. That’s a error because the case had not been tried, nor a verdict determined at the time of the ABFO exam. The legal crux of this matter is simple. Each board certification applicant who took the ABFO exam completed a detailed analysis of the Ridley evidence, wrote extensive reports for the ABFO testing committee, and gave oral presentation of their findings. The defense counsel argued in court its legal right to see these reports. A subpoena for these heretofore-unknown reports was submitted by the defense and placed before the judge. The prosecution objected and a hearing was then held, which is the source of this post’s information.

The prosecutor in this case who responded to the subpoena, spoke to the judge and represented the prosecution’s and the ABFO’s objections to the release of these reports. Evidently the reports submitted for board certification were contrary to the prosecutions expert. In a real science if the prosecution’s dental expert made a mistake and published the bitemark evidence (only photos and dental models; no other documentation from the case were included and teeth models of a second fictitious suspect were included for the exam), then the forensic group should admit to the error and agree to the legal right of the court and the defendant to examine the additional reports written by board eligible dentists, who are all now board certified dentists.

The judge heard both sides, and in telephone testimony from the prosecutor’s expert confirmed that these extra judicial reports existed. In a surprise revelation, most or all of the reports did not concur with either the prosecutorial dentist’s opinion or the reports from the two additional dentists who rendered second opinions on the behalf of the prosecution’s dentist. Subsequent to these revelations, the judge granted the subpoena and ordered the ABFO to produce all reports and materials germane of the four applicants.

In a communication to the defense counsel in a last ditch effort to minimize the impact of the findings, the two past ABFO presidents who were tasked with obtaining and divulging the exam reports and evidence, commiserated once more on their objections to the subpoena. Their reasoning, in part, is this statement:

The candidates were required to show how their opinions were formed and evaluated on their ability to present the facts of the constructed case, communicate and demonstrate their analysis methods, and defend their conclusions.

Again, this was a created and fictitious case scenario. No “right” or”wrong” conclusions existed. The candidates were not graded on the absolute “correctness” of their opinions but rather on the processes they utilized to reach those conclusions.

There was no intent or attempt to make this examination scenario identical or similar to any existing actual casework.

Understanding actual bitemark cases and the use of limited information about a patterned injury in skin as a board examination are vastly different. Thus, it is not appropriate to compare the two processes.

Now, am I missing something here? The physical evidence materials for the ABFO bitemark exam were taken from an actual case that had not been tried yet. The use of a case’s extraneous documentation and circumstantial information should be withheld from a forensic examiner (fingerprint, firearms, DNA to name a few) until after the physical analysis is complete. Yet the ABFO appears to differ with this protocol and clearly state that all this extra information is necessary to render a final opinion on the analysis of physical evidence. Therefore, the ABFO bitemark exam is not representative of actual casework or the practice of bitemark identification.

How vastly different is forming an opinion on limited information on a patterned injury in skin from forming an opinion in an actual case? This was material from an actual case. If it is not appropriate to compare the processes, then what benefit does the ABFO applicant gain by completing the examination? If all that is important is following a process to form an opinion, and the correctness of the answer is unimportant, then what value is ABFO certification for the trier of fact?

Does the Forensic Science Advisory Board of the American Academy of Forensic Science know about this? This is the parent organization that certifies the ABFO. I t certainly should, because one of the ABFO past presidents who wrote the above quote is Secretary of the FSAB. The FSAB might also like to know that the results of the examination were destroyed, against the standards of the FSAB.

So the much embattled American Board of Forensic Odontology (ABFO), continues its uphill fight to preserve its courtroom credibility by offering direct support for the continued prosecutorial use of their Congressionally debunked and scientifically untested bitemark comparison opinions. The ABFO continues to orchestrate its membership down the unacceptable path of prosecutorial partisanship.