By Dr. C. Michael Bowers
The impending July 7, 2011 execution of Mexican national Humberto Leal (http://www.npr.org/2011/06/15/137202798/planned-texas-execution-has-mexico-up-in-arms) 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.