A previous blog from CSI DDS stated that poor bite mark reliability (how often experts agree) is proof of the suspect nature of the outdated methods stubbornly maintained by leaders of the ABFO. Their opposition to review of its membership’s casework is well established and contrasts with the efforts of the FBI in reviewing their cases involving microscopic hair analysis. The dentists prefer to attack each other to put the blame on “bad apples” rather than their inadequate methods.
In early 2008 Professor Iain Pretty and myself undertook a personal review of bite mark casework I had participated in from 2000 to 2007. This research was the initial attempt to establish a relationship between the forensic “value” of the injury patterns admitted by prosecution bite mark experts and the courts’ outcomes. The link at the end will bring you to the 2008 AAFS presentation of our findings. The case categories varied
- pre trial cases where I was a defense expert retained as a defense expert
- trial cases where I participated as a defense expert
- post-conviction ( appellate) cases where I reviewed bite mark evidence used by the prosecution
- post-conviction cases where new DNA profiling was used to argue actual innocence of the defendant (exoneration litigation)
Case types included assaults, homicide, rape, and child abuse.
The first hurdle was to apply a system that could categorize the various injuries presented in the casework. Since the ABFO has no standards to quantify the forensic value of an alleged bitemark injury, this leaves the determination up to the personal opinion of each bite mark examiner. Dentists continue to argue the value of “one tooth” bite marks. (NYC). This is just one of the uncontrolled and speculative aspects of bite mark opinions that are brought to court. The other assumptions used by the ABFO in court such as “uniqueness” of each person’s teeth and the accuracy of skin to mimic a biter’s teeth were not considered in this case review. However, most of the cases probably had the prosecution expert using them to their advantage. Much like the recent admissibility hearing on a bite mark in NYC.
Professor Pretty had created such a scale system in 2007 and had tested it on police officers (in the UK) and published the results in the Journal of Forensic Sciences in 2007. He called it BMSSS (Bite Mark Severity and Significance Scale). Numerical values (named “significance” in the study) were established on a continuum of 1 through 6 (How it works: This ranges from low detail significance (1-2) to higher detail (3- 4), and then declining detail (5-6) because of deep lacerations and tissue injuries (i.e. too much damage). Dr. Pretty determined the BMSSS values for 48 cases without knowing any case information. Note: Slide 4 shows the BMSSS scale. There also are graphs that compare bite mark “significance” with 1) expert agreement 2) judicial outcome 3) case types.
Slide 13 is the kicker. The forensic value of prosecution bite marks later debunked by post-conviction DNA are the SAME as the bite mark cases without available DNA used for conviction. Both have categories and BMSSS values of 1.8 (the lower end of the BMSS). So, when a dentist uses “medical certainty” in a bite mark opinion the gatekeeper (i.e. the judge) better watch out.
The bad apple theory used by the ABFO is a “red herring” (a statement made to avoid the real facts of the case).