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Bite-mark verdict faces new scrutiny
Thelma Younkin used an oxygen tube to help her breathe. Her killer used it as a murder weapon.
In November 1991, the frail, 65-year-old Younkin was strangled with the tube, bitten and raped in her room at the Post Park Motel along a grim stretch of this desert town.
A fellow resident of the low-budget motel, Bobby Lee Tankersley, was convicted and sent to Arizona's Death Row for the attack, based largely on the testimony of a forensic dentist who said he had matched Tankersley's teeth to bite marks on Younkin's body.
But on Monday, the same judge who sentenced Tankersley to death will hold a hearing that promises to showcase the problems of forensic science in America's courts, from the legacy of discredited experts to new DNA tests exposing the questionable science behind many other disciplines, including bite-mark comparison.
Tankersley was granted Monday's hearing largely because the forensic dentist who was key to his conviction also was at the center of perhaps the nation's most noted case of mistaken bite-mark testimony.
Dr. Raymond Rawson's opinion helped send an innocent man, Ray Krone, to Arizona's Death Row. At Krone's 1992 trial, Rawson said bite marks on a murdered Phoenix cocktail waitress were "a very good match" to Krone's teeth. Rawson also testified during Krone's 1996 retrial that his teeth were "a scientific match" to a spotty pattern of blood on the victim's bra.
Krone, a former postal worker, spent more than a decade in prison before DNA testing proved Rawson wrong, connecting another man to the murder and exonerating Krone. Just last week, Krone, who had been dubbed "the snaggletooth killer," had his teeth redone courtesy of the ABC television show "Extreme Makeover," according to his attorney, Christopher Plourd, who is advising Tankersley's lawyers.
Increasingly, other forensic dentists are questioning whether such definitive declarations can be made about bite marks left in skin, let alone based on blood patterns on clothing.
State prosecutors were so concerned about the similarities in Rawson's testimony at the two men's murder trials that on the day Krone walked free in April 2002, they asked the Arizona Supreme Court to order new DNA tests on evidence from the Tankersley case.
The results of those tests will be central at the hearing scheduled for Monday in the courtroom of Yuma County Superior Court Judge Thomas Thode. But they are more ambiguous than the tests that exonerated Krone by matching another man who is now scheduled to stand trial next year.
Tankersley's attorneys plan to argue that the tests in his case--on everything from the oxygen tubing used to choke Younkin to swabs of the marks left on her body--exclude Tankersley and reveal the genetic profile of someone else.
"We have a clear profile from a male in many of the samples that's not Tankersley," said attorney Jennifer Sparks, who is representing him. "That's kind of hard to explain if you're the state."
Prosecutors, however, contend that those same tests actually provide more convincing proof of Tankersley's guilt. They also say the genetic evidence might have been contaminated during the handling of Younkin's body after the killing.
According to the Arizona Department of Corrections, Younkin's grandson owed Tankersley, who was 39 at the time of the murder, money for drugs, and Tankersley had told Younkin's daughter before the murder that the grandson would "live to regret it" if he did not meet with him.
"If the evidence was such that it was clear that Tankersley didn't do it, then we wouldn't be having this hearing," said John Todd, the assistant Arizona attorney general who initially asked for the new testing. "But that's not the case. In the [state] criminalist's view, in fact, it looks like it's more certain that he is the guy."
The DNA evidence in question is open to interpretation because some of the samples indicate multiple genetic profiles. But the test results weren't complete enough, according to Tankersley's lawyers, to run through FBI databases that in theory could connect Younkin's murder to someone else.
Even Todd acknowledged that "with mixed samples, it's very difficult to be absolutely conclusive" about including a suspect.
When Tankersley was put on trial in 1993, Dr. Ed Blake, a prominent DNA analyst, testified that the DNA profile taken from a hair found in the sink of Younkin's motel room was consistent with Tankersley's genetic profile but also found in about 4 percent of the Caucasian population.
While not conceding the hair is Tankersley's, his appellate attorneys have downplayed its significance because he knew Younkin and lived in the same motel.
That left the state with bite-mark testimony from Rawson. He used a video presentation, including fade-in and fade-out techniques, to convince jurors that all of the marks on Younkin's body matched Tankersley's teeth.
But according to the motion to exonerate filed last month by Tankersley's lawyers, the state's other expert at trial, Dr. Norman Sperber, "could not identify any individual characteristics of teeth whatsoever in the marks on the neck, ear, chin, and jaw area. The techniques of Dr. Rawson were questionable, his video presentation misleading, and his conclusions highly dubious"
Rawson could not be reached for comment. His assistant, Linda Chapman, said that he had retired in March from doing forensic dentistry and that "he doesn't want to discuss the case."
A prominent Nevada state legislator as well as a dentist, Rawson lost in the Republican primary this year partly, some observers say, because of news coverage of his role in the Krone case.
In the Tankersley trial, the defense did not present a dental expert to refute Rawson.
The state made his bite-mark testimony central to its closing argument.
"This defendant, in essence, signed his name to the body of his victim," prosecutor Mary White told the jury.
When Thode sentenced Tankersley to death in May 1994, he cited the bite marks as evidence that the crime was heinous and depraved.
Since then, however, other forensic dentists working with the defense have challenged Rawson's testimony in the case. Among them are Dr. Richard Souviron, the chief forensic odontologist for the Miami-Dade County medical examiner's office. Souviron, who has testified for prosecutors and defense attorneys in other cases, questioned whether all the marks on Younkin's body were bite marks.
"She had a human bite mark on her left breast," Souviron said. But "Dr. Rawson came up with a bite mark on the chin and the right breast," among other places. "They were bruises. They definitely, in my opinion, were not bite marks."
Expert is doubtful
Another odontologist, Dr. Michael Bowers, who served on the examination and credentials committee of the American Board of Forensic Odontology, submitted an affidavit for Tankersley's defense. In it, he reiterated his skepticism about the entire discipline of bite-mark comparison.
"The serious deficiencies of the `science' of bite marks make its use as an identifier of a single perpetrator a very dangerous proposition," Bowers wrote.
Noting the disagreement between Sperber and Rawson, Bowers added, "The divergence of opinion between the state's own dental experts in Tankersley is another anecdotal indicator of [the] weak reliability and foundation of bite-mark identification."
As part of a recent series on forensic science in the courtroom, the Tribune examined 154 criminal cases involving bite-mark evidence, mostly murders and rapes, that reached appeals courts in state and federal jurisdictions around the country. In more than a quarter of those cases, the prosecution and defense offered forensic dentists who gave diametrically opposed opinions.
The discrediting of Rawson's testimony in the Krone case is one of numerous instances in which leading practitioners of bite-mark comparison have erred.
Monday's hearing on the Tankersley case, however, is expected to focus less on the marks left on Younkin's body than the DNA evidence swabbed from them.
Since Blake's testimony in Tankersley's trial, DNA technology has advanced greatly. After Krone's exoneration, more sophisticated tests were performed on swabs taken from marks on Younkin's body, fingernail clippings from her hands, the oxygen tubing and cigarette butts recovered from the crime scene.
Just what those tests yielded is a matter of dispute. There will be at least three interpretations--from an Arizona Department of Public Safety analyst, private lab Orchid Cellmark and an expert appointed by the court for Tankersley.
They have varying degrees of disagreement on whether the tests help or hurt his argument that he is innocent.
One thing that is not in dispute: DNA from at least three people was found on the oxygen tubing--the murder weapon--but Tankersley's genetic profile isn't among them.
"If Mr. Tankersley was the true perpetrator of this crime, then his DNA should have been found on the murder weapon," his attorneys wrote in their motion to exonerate.
But Todd, the assistant attorney general, noted that Cellmark concluded that Tankersley could not be excluded as a possible source of DNA found in alleged bite wounds to Younkin's face and right breast.
Hope for retrial
After this week's hearing, which is expected to last a couple of days, the judge will hold a hearing Dec. 13 to give the state a chance to respond. Tankersley is hoping for a new trial, if not outright exoneration.
Back at the Post Park, doubts linger over whether he was responsible for Younkin's rape and murder. The motel and the adjacent Desert Sands are all that are left of the long skid row of places that attracted many transients around the time she was killed.
Her former home, No. 9, is one of a dozen stucco and cinder-block rooms filled mostly with older residents on disability who pay by the month. Back in 1991, anybody with a little cash could have a room for $15 or $20 a night.
"There was a bunch of speed freaks around here, especially back then," recalled Tom Poston, a retired strawberry picker and carnival worker who said he moved out of the Post Park a few months before Younkin was killed but has since returned. "It could've been anybody."