Chicago Tribune, July 10, 2008
Guilty, said bite expert.
As forensic scientists scramble to shore up a shaky field, new evidence casts doubt on an old conviction
By Maurice Possley and Steve Mills
In 1985, Robert Stinson was convicted of murder largely on the basis of bite-mark testimony. Two decades later, DNA points to someone else.
MILWAUKEE — In a cubicle at Marquette University, a professor of dentistry and a former prosecutor are trying to use computer science to shore up a beleaguered forensic discipline.
But as the two men try to lay the groundwork to provide a statistical backbone to preserve bite-mark comparison's place in the courtroom, they are being confronted with new evidence from a 1984 murder case that suggests their own use of this controversial analysis may have sent an innocent man to prison.
Dr. L. Thomas Johnson, a veteran forensic odontologist —or dental scientist—at Marquette, and a colleague, law professor Daniel Blinka, worked together on that criminal case, the first in Wisconsin to use bite-mark evidence. Blinka was the prosecutor who brought the charges, and Johnson testified that the bite marks on the victim were made by Robert Stinson.
Stinson, who has always insisted he was innocent, now has new hope to win his freedom: DNA tests exclude him as a source of saliva found on the victim, and a defense-commissioned study concludes the testimony from Johnson and another forensic dentist was inaccurate.
His case, as well as Johnson's new research, raises a question that has been asked frequently in recent years: Can bite-mark comparison be trusted or is it a junk science?
Johnson and Blinka stand behind their work in the Stinson case and insist that bite-mark analysis is credible.
"What we want to show," Johnson said during an interview at Marquette's dental school, "is that it's not a faulty science if it's done properly, and there is a solid statistical basis behind it."
Johnson said his and Blinka's new research was prompted in part by a 2004 Tribune series, "Forensics Under the Microscope," that showed that DNA tests have proved wrong many of the leading bite-mark experts, including the discipline's founding fathers.
One of them, Dr. Raymond Rawson, helped send two men to Death Row in Arizona, and in both cases his work was later undermined, with one of the men set free. He also testified against Stinson.
The Tribune in its series also examined 154 cases involving bite-mark comparison, mostly murders and rapes, that reached appeals courts around the country and found that, in more than one-quarter of the cases, forensic dentists for the prosecution and defense gave diametrically opposed opinions.
Johnson's research aims to provide scientific underpinning to the much-criticized discipline by establishing a database similar to the fingerprint database. Johnson believes that if a sufficient number of images of sets of teeth are put into a computer, all with consistent marking points, forensic dentists could estimate the frequency of dental patterns.
For the study, Johnson gathered dental molds from more than 400 Air National Guard members and scanned them into a computer. He then established six identifying characteristics.
"This is only a starting point," Johnson said. "This isn't the Rosetta stone that's going to solve all the problems. We're not ready for prime time yet. But what it's done is answered the question of whether there is any science behind this."
David Sweet, a professor of odontology at the University of British Columbia who has been working on a similar study, said Johnson's research is much needed.
"Right now it's a discipline based on an opinion," Sweet said. "But in order to express that opinion in real terms, what we need to know is if anybody in the population has the same dental traits as the suspect."
Other odontologists are skeptical, saying Johnson's study sample is too small and does not represent the wider population. Any conclusions drawn from it, they say, would be misleading.
"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."
Over the past two years, as Johnson was doing his research, lawyers for Stinson were uncovering new evidence in the 1984 murder of 63-year-old Ione Cychosz, who was beaten to death and bitten eight times. Stinson was sentenced to life in prison for Cychosz's murder.
The DNA test results — from saliva on Cychosz's sweater — and the study from four other bite-mark experts have been turned over to Milwaukee County prosecutors for their review. Stinson's attorney, Byron Lichstein of the Wisconsin Innocence Project, has asked prosecutors to vacate Stinson's conviction. He is scheduled to meet with the prosecutors Thursday.
"At this point, we feel there is more review that needs to be done in this case before any decision is made," said John Chisholm, Milwaukee County district attorney.
Johnson examined Cychosz's body the day it was found nude and battered near her home. He worked with a police sketch artist to come up with a diagram of the attacker's teeth and determined that the suspect had a missing upper front tooth.
A detective on the case, James Gauger, who has since retired, recalled in an interview that after Johnson said the perpetrator had a missing tooth, he and his partner visited Stinson's home as part of their neighborhood canvass. Stinson lived in a home adjacent to the yard where the body was found.
"My partner told him a couple of jokes, and Stinson laughed," Gauger said. When they saw a missing tooth, "we knew we had our man."
After Johnson said he had linked Stinson's teeth to the bite marks and Rawson concurred, Stinson was arrested.
"I was an easy target," Stinson, now 43, said in a recent interview at the New Lisbon Correctional Institution. "I was young. I had no education, and they took advantage of that."
At his three-day trial in December 1985, Stinson insisted he was innocent. The only evidence against him was the bite-mark testimony. Neither Johnson nor Rawson used any of the qualifying language that experts in the field say bite-mark analysts should use when testifying.
Johnson concluded the bite marks on Cychosz "had to have been made by teeth identical" to Stinson's and there was "no margin for error in this." Rawson called the evidence "overwhelming" and said "there was no question there was a match."
Three years ago, Stinson wrote to the Wisconsin Innocence Project at the University of Wisconsin Law School. After taking his case, Lichstein, working with the cooperation of Milwaukee County prosecutors, obtained the DNA tests and commissioned the review of Johnson and Rawson's findings.
The group was headed by Gregory Golden, current chairman of a committee of the American Board of Forensic Odontology that oversees guidelines for the use of digital imaging in bite-mark analysis — a tool that has improved the ability of odontologists to compare bite marks.
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, in an interview, defended his work in the case and said he has seen nothing to suggest Stinson is innocent. "I would have to say that I respectfully disagree with them," he said.
Rawson declined to comment.
Blinka also rejected the report. "As I sit here now, do I have any reasonable doubt that Stinson is guilty?" he said. "No, I don't."
Stinson, meanwhile, said he has been told that he cannot qualify for parole unless he admits guilt.
"But I won't do it. I'm innocent," he said. "This is a huge mistake. I am not a murderer. I'm an innocent person that wants his freedom back."