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.
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.
Injecting scienceJohnson'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.