Faulty bite mark evidence has played a part in at least five wrongful convictions later overturned by DNA testing. Robert Stinson in Wisconsin could become the sixth. New DNA testing indicates that Stinson is in prison for a murder he didn’t commit and his case is again calling the field of forensic dentistry into question.
Dr. L Thomas Johnson, a Wisconsin bite mark analyst, testified at Stinson’s trial for a 1984 murder that bite marks on the victim’s body matched Stinson’s teeth. Now, DNA testing on saliva from the victim’s shirt have shown that another man left the bite marks. The Wisconsin Innocence Project, which represents Stinson, has filed for his release based on the new evidence.
While Johnson stands behind his work in the Stinson case, other forensic dentists have found not only that Johnson’s analysis was wrong, but also that he went too far in saying that there was “no doubt” the bite marks came from Stinson.
The case also was examined by forensic experts from Texas, California and Illinois. In their report, the experts said that while some modern methods were not available in 1984, "it should be emphasized that Drs. Johnson and Rawson should have excluded Robert Lee Stinson even based on methods and standards available at the time … because there is little or no correlation of Robert Lee Stinson's dentition to the bite marks."
The report also criticized Johnson's testimony that there was no doubt Stinson's teeth left the marks. "That statement has no evidence-based, scientific, or statistical basis and drastically overstates the level of certainty attainable using bite mark analysis," the report said.
Johnson is also leading a project to build a computer database of bite marks, attempting to bring scientific rigor to a discipline that has been criticized for lacking it. He says his research shows that bite marks have six distinct identifying points that distinguish them. But other forensic dentists are skeptical of his work.
"This is the epitome of junk science cloaked as academic research," said Dr. Michael Bowers, a California odontologist and a frequent critic of bite-mark comparisons. "I don't think his claims are supported. The study just doesn't pass muster."
Read the full story here
. (Chicago Tribune, 07/10/08)
The Innocence Project has called for scientific oversight in all forensic fields, and has criticized bite mark analysis for years because there are no national standards or acceptable certification procedures. Earlier this year, two Innocence Project clients originally convicted based on bite mark comparison – Kennedy Brewer and Levon Brooks – were exonerated when DNA testing led investigators to the real perpetrator of the murders for which the two men had been convicted.
Read more about wrongful convictions overturned by bite mark evidence here