In May 1992, the body of three-year-old Christine Jackson was found in a creek in Noxubee County, Mississippi. She had been taken from her home, raped, and murdered. Police arrested Kennedy Brewer, the mother’s boyfriend, largely ignoring a broken window near the child’s bed that could have allowed an intruder.
The case against Brewer rested on 19 marks found on the child’s body. Medical examiner Steven Hayne called them bite marks. Forensic odontologist Dr. Michael West examined them and declared, with what he called absolute certainty, that the marks belonged to Brewer’s teeth “indeed and without a doubt.”
Brewer was convicted and sentenced to death.
He spent 15 years in prison, seven on death row. In 2008, DNA evidence finally proved his innocence. The marks on Jackson’s body were likely left by crawfish that fed on her body in the creek. Not teeth. Certainly not Brewer’s teeth.
Brewer’s case is not an outlier. It is a pattern. At least 36 people have been exonerated after wrongful convictions based on bite mark analysisA forensic technique in which distinctive patterns left by human teeth on skin or objects are compared to a suspect's dental impressions to establish identity or involvement in a crime.. Some spent decades on death row. Others remain in prison today, despite the fact that four separate governmental scientific bodies have concluded the technique has no basis in science.
How Bite Marks Entered the Courtroom
The story begins with a block of cheese. In 1954, a grocery store in the small West Texas city of Aspermont was burgled. Police found a piece of cheese with teeth marks left by the intruder. A firearms examiner photographed the impressions, made plaster casts, and concluded they matched the suspect’s teeth. The Texas Court of Criminal Appeals upheld the conviction in Doyle v. State, and bite mark evidence entered American jurisprudence through the side door.
From cheese to skin. From burglary to murder. Over the following decades, forensic odontologists built an entire discipline on two foundational claims: that every person’s dental pattern is unique, and that human skin reliably records those patterns. Neither claim has ever been scientifically validated.
The Human Cost
The names form a grim catalog. Each one represents years, sometimes decades, that no apology can return.
Ray Krone was a postal worker in Phoenix with no criminal record. When a bartender he knew was found murdered in 1991, police asked Krone to bite into a Styrofoam block. Prosecutors’ experts said the bite marks on the victim matched. The media dubbed him the “Snaggletooth Killer.” He was sentenced to death. DNA testing in 2002 proved his innocence and identified the real killer, Kenneth Phillips, who lived near the bar and had never been considered a suspect. Krone spent more than 10 years in prison, including time on death row. He became the 100th death row inmate freed since the reinstatement of capital punishment in 1976.
Keith Allen Harward was a sailor in Newport News, Virginia, when a woman was raped and her husband murdered in 1982. The assailant wore a Navy uniform and bit the victim’s legs. Harward was among a group of sailors required to give dental impressionsA physical mold of the teeth made by pressing them into a soft material, used in forensic analysis to compare tooth shapes against bite marks found at a crime scene.. Six forensic dentists, including two who testified at trial and two hired by the defense, all agreed his teeth matched the bite marks. Two of them told the jury this was true “to a scientific certainty.” Every single one of them was wrong. DNA evidence in 2016 pointed to another sailor, Jerry Crotty. Harward had spent 33 years in prison.
Eddie Lee Howard, a Black man in Columbus, Mississippi, was sentenced to death in 1994 for the murder of an elderly white woman. The conviction rested almost entirely on bite mark testimony from the same duo who had condemned Brewer: Hayne and West. Initially, Hayne did not report seeing bite marks on the body. But after the prosecutor identified Howard as the primary suspect, Hayne said he had seen marks that could be bite marks. The victim’s body was exhumed, and West proclaimed the marks matched Howard. Howard spent 26 years on death row before DNA testing excluded him and the Mississippi Supreme Court vacated his conviction in 2020.
Levon Brooks, convicted of a strikingly similar crime in the same Mississippi county two years before Brewer, also based on West’s testimony. He served 16 years before being exonerated alongside Brewer in 2008.
Steven Chaney served 28 years in Texas for a murder conviction that relied on bite mark testimony from two forensic dentists. He was officially exonerated by the Texas Court of Criminal Appeals.
Bill Richards spent nearly 23 years in a California prison after a forensic dentist said a wound on his wife’s hand matched his teeth. The California Supreme Court eventually threw out the conviction.
Still Behind Bars
Not everyone has been freed. Charles McCrory has spent more than 38 years in an Alabama prison for the murder of his wife. The bite mark expert in his case, Dr. Richard Souviron, recanted his testimony, saying he now knows he cannot say whether a bite mark on the victim matched McCrory’s teeth. Yet Alabama’s courts have declined to free him. The Court of Criminal Appeals ruled that the jury was capable of deciding on its own whether the marks matched, a finding that ignores the scientific consensus that such visual matches cannot be valid.
McCrory has twice refused plea deals that would have set him free in exchange for a guilty plea. “I refused to take it because I didn’t kill her,” he told NBC News. “I did not kill my wife.”
The U.S. Supreme Court declined to hear his case in 2024.
As forensic dentist Adam Freeman, who once practiced bite mark analysis before rejecting it, told NBC News: “I can tell you that literally thousands of human years have been spent in jail” based on faulty testimony.
The Science That Never Was
The scientific case against bite mark analysis is not a matter of debate among researchers. It is settled. The technique fails on every foundational premise.
In 2009, the National Academy of Sciences published Strengthening Forensic Science in the United States: A Path Forward, which found “no evidence of an existing scientific basis for identifying an individual to the exclusion of all others” through bite mark comparison. The report documented “substantial rates of erroneous results” and highlighted the discipline’s complete lack of scientific validation.
In 2016, the President’s Council of Advisors on Science and Technology (PCAST) was more direct: “PCAST finds that bitemark analysis does not meet the scientific standards for foundational validity, and is far from meeting such standards.” The council advised against investing in trying to validate the method, concluding the prospects were too low.
In 2022, the National Institute of Standards and Technology (NIST), the gold standard of measurement science, published a comprehensive review of more than 400 publications and found that all three foundational premises of the discipline are unsupported by data: human dental patterns have not been shown to be unique, those patterns do not transfer accurately to skin, and examiners cannot reliably analyze the resulting marks.
One 2016 study found that practitioners could not even distinguish between human and animal bite marks.
Where Things Stand
Despite the overwhelming scientific rejection, no court has categorically ruled bite mark evidence inadmissible. The technique has been used in thousands of cases. While its use has declined steeply, prosecutors still sometimes attempt to introduce it at trial.
The American Board of Forensic OdontologyThe branch of forensic science that applies dental knowledge to legal investigations, including identifying individuals through bite marks or dental records. changed its guidelines in 2016, no longer permitting conclusions of “exact match.” The strongest statement now allowed is that a person is “not excluded as having made the bitemark.” Professional associations have argued that the misidentifications occurred in the 1980s and 1990s and that today’s standards are different.
Critics counter that the fundamental problem remains unchanged: the discipline was never scientifically validated in the first place, and no amount of revised guidelines can fix a method built on unproven premises.
Six states have adopted “change in science” statutes or court rulings that allow people convicted on discredited forensic evidencePhysical evidence collected from a crime scene and analyzed scientifically to establish facts or reconstruct events; includes biological materials, trace evidence, and physical objects examined by forensic specialists. to bring their cases back to court: California, Connecticut, Michigan, Nevada, Texas, and Wyoming. The Texas Forensic Science Commission issued a moratorium on bite mark evidence in 2016, the first such action by any governmental body.
For the wrongfully convicted who have been freed, the aftermath is its own sentence. Keith Harward, now living in North Carolina, still struggles with what happened to him. “It’s garbage. It’s crap. It doesn’t mean anything,” he told NBC News of the bite mark evidence that cost him half his life.
For Charles McCrory, entering his 39th year in an Alabama prison, the wait continues. “I don’t give up hope,” he said. “You can’t give up. That’s just not an option.”
In May 1992, the body of three-year-old Christine Jackson was discovered in a creek approximately 500 yards from her home in Noxubee County, Mississippi. She had been abducted from her home during the night, sexually assaulted, and killed. Investigators noted no signs of forced entry but also documented a broken window near the child’s bed that could not be locked. Despite this, police arrested Kennedy Brewer, the mother’s boyfriend.
The prosecution’s case centered on 19 marks found on Jackson’s body. Medical examiner Steven Hayne classified them as bite marks and called in forensic odontologist Dr. Michael West to examine them. West testified that the marks came from teeth and that those teeth belonged to Brewer “indeed and without a doubt,” excluding all other possible sources. This degree of certainty is unsupported by any existing scientific framework for bite mark identification.
Despite conflicting testimony from another forensic dentist, Brewer was convicted and sentenced to death. He spent 15 years in prison, seven on death row. DNA testing eventually proved his innocence. The marks on Jackson’s body were likely left by crawfish feeding on her remains in the creek.
Brewer’s case is representative of a systemic failure. At least 36 people have been exonerated after wrongful convictions based on bite mark comparisons. Four governmental scientific bodies have concluded the technique has no basis in science. Yet bite mark evidence has been used in thousands of criminal prosecutions, and no court has categorically ruled it inadmissible.
The Three Failed Premises
Bite mark analysisA forensic technique in which distinctive patterns left by human teeth on skin or objects are compared to a suspect's dental impressions to establish identity or involvement in a crime. rests on three foundational claims. The National Institute of Standards and Technology’s 2022 scientific foundation review, which examined more than 400 publications, found that none of them are supported by data—a pattern that echoes broader problems with scientific research reproducibility.
Premise 1: Human Dental Patterns Are Unique
Bite mark analysis assumes that each person’s dentition is as unique as a fingerprint. NIST found no studies establishing the uniqueness of human anterior dental patterns at the individual level. No population studies have been conducted to identify distinguishing features of biting surfaces or estimate how common or rare specific dental characteristics are. The assumption of uniqueness was adopted by the field without empirical validation.
Premise 2: Skin Reliably Records Dental Patterns
Even if dental patterns were unique, human skin is a poor recording medium. As forensic dentist Adam Freeman explained: “What we’re looking at isn’t actually a bite mark indentation, we’re looking at the bruise that’s left over. And a bruise doesn’t exactly approximate the teeth that made it because bruises are diffuse areas of blood under the skin.”
Skin elasticity varies by age, body composition, and location on the body. Skin holds tension differently depending on movement. NIST noted that bitemarks can be distorted by skin elasticity, victim movement during the bite, and post-injury swelling and healing. These variables mean the same set of teeth could produce different marks on different people, or different marks on the same person at different times.
Freeman noted that the necessary studies on living subjects will likely never be conducted: “You’re never going to get approval to do a study where you say, I’m going to bite 1,000 people and some of those people are going to have cancer or diabetes or sickle cell anemia.”
Premise 3: Examiners Can Accurately Analyze the Marks
In a study conducted by Drs. Iain Pretty and Adam Freeman (Freeman was then president-elect of the American Board of Forensic OdontologyThe branch of forensic science that applies dental knowledge to legal investigations, including identifying individuals through bite marks or dental records.), ABFO-certified dentists were asked to analyze photographs of 100 injuries using a standardized “decision tree.” They were asked basic questions: Was the injury a bite mark? Was it suggestive of a bite mark? Was it not a bite mark? In all but a few cases, the practitioners could not agree on the answers—a phenomenon that reflects deeper issues with expert consensus in fields lacking solid foundations.
“That was so horrifying,” Freeman said. “If experts can’t agree on the answer to that initial question: Is this or is this not a bite mark? That should trouble anybody.”
A separate 2016 study found that self-described experts could not reliably distinguish between human and animal bite marks.
The Institutional Response: A Timeline
2009: National Academy of Sciences. The NAS report Strengthening Forensic Science in the United States: A Path Forward documented “substantial rates of erroneous results” in bite mark analysis and found “no evidence of an existing scientific basis for identifying an individual to the exclusion of all others” through bite mark comparison.
2016: President’s Council of Advisors on Science and Technology (PCAST). The council’s report stated that “bitemark analysis does not meet the scientific standards for foundational validity, and is far from meeting such standards.” It added: “available scientific evidence strongly suggests that examiners cannot consistently agree on whether an injury is a human bitemark and cannot identify the source of bitemark with reasonable accuracy.” PCAST advised against investing resources in trying to validate the method.
2016: Texas Forensic Science Commission. After a six-month investigation, the commission issued a moratorium on the use of bite mark evidence in Texas prosecutions and ordered a review of past cases. This was the first such action by any governmental body.
2016: American Board of Forensic Odontology. The ABFO revised its guidelines, no longer permitting conclusions of “exact match” or that a perpetrator made a mark “without a doubt.” The strongest conclusion now allowed is that a person is “not excluded as having made the bitemark.”
2022: National Institute of Standards and Technology. NIST’s scientific foundation review concluded that “forensic bitemark analysis lacks a sufficient scientific foundation” and that all three key premises of the discipline are unsupported by data.
Case Studies: The Evidence Chain
Keith Allen Harward (Virginia, 1982-2016)
A 1982 home invasion in Newport News resulted in a murder and rape. The attacker wore a Navy uniform and bit the victim’s legs. Keith Harward was among sailors from the USS Carl Vinson required to give dental impressionsA physical mold of the teeth made by pressing them into a soft material, used in forensic analysis to compare tooth shapes against bite marks found at a crime scene.. A dentist initially excluded him, but he became a suspect six months later after his then-girlfriend reported he had bitten her during a dispute.
At trial, forensic dentists Lowell Levine and Alvin Kagey testified that Harward’s teeth matched the bite marks “to a scientific certainty.” Levine had served as president of the American Academy of Forensic Sciences, the American Board of Forensic Odontology, and the Forensic Sciences Foundation. Six forensic dentists in total, including two retained by the defense, agreed the marks matched Harward.
The Innocence Project later discovered that a security guard’s identification of Harward occurred only after the witness was placed under hypnosis, and that blood evidence actually excluded Harward rather than being inconclusive as the prosecution claimed.
DNA testing identified Jerry Crotty, a sailor on the same ship with a violent criminal record, as the actual perpetrator. Harward was exonerated in 2016 after 33 years. All six dental experts had been wrong. Unlike bite mark analysis, genetic evidence when properly collected and analyzed provides the reliable identification that forensic dentistry claimed to offer.
Ray Krone (Arizona, 1992-2002)
Kim Ancona, a 36-year-old bartender, was found murdered in a Phoenix bar in December 1991. The prosecution’s case against regular patron Ray Krone rested entirely on bite mark evidence. Experts testified that marks on the victim’s body matched Styrofoam impressions of Krone’s teeth. His irregular teeth earned him the media nickname “Snaggletooth Killer.”
Krone was sentenced to death. He won a new trial on appeal in 1996 but was convicted again on the same bite mark testimony. The judge, citing doubts about Krone’s guilt, sentenced him to life rather than death.
DNA testing in 2002 excluded Krone and matched Kenneth Phillips, a man incarcerated for an unrelated sex crime who lived near the bar and had never been investigated. Phillips did not have irregular teeth. Krone became the 100th death row exoneree since 1976.
Eddie Lee Howard (Mississippi, 1994-2021)
Howard was convicted in 1994 of the rape and murder of an 84-year-old woman in Columbus, Mississippi. The conviction relied on testimony from Steven Hayne and Michael West, the same pair who testified in the Brewer and Brooks cases. Hayne did not initially report bite marks on the victim’s body. After the prosecutor identified Howard as the primary suspect, Hayne revised his assessment. The victim’s body was exhumed and examined by West, who proclaimed the marks matched Howard.
West was subsequently suspended from the ABFO and later forced to resign from the American Board of Forensic Pathology. When Howard’s appeal reached the Mississippi Supreme Court in 2006, the court wrote of West’s testimony: “Just because Dr. West has been wrong a lot, does not mean, without something more, that he was wrong here.”
DNA testing eventually excluded Howard. The Mississippi Supreme Court vacated his conviction in August 2020, and he was exonerated in January 2021 after 26 years on death row. He was one of four Mississippians whose death row convictions were overturned due to the same discredited forensic methods.
Charles McCrory (Alabama, 1985-present)
McCrory was convicted of murdering his wife, Julie Bonds, in 1985. The key evidence was testimony from Dr. Richard Souviron, who gained fame as an expert after testifying in the trial of serial killer Ted Bundy. Souviron said two marks on the victim’s shoulder matched McCrory’s teeth.
Nearly 35 years later, Souviron recanted, writing in an affidavit that modern science has exposed the limitations of bite mark evidence. Alabama’s courts have declined to grant a new trial. The Court of Criminal Appeals ruled the jury was capable of deciding on its own whether the marks matched. The U.S. Supreme Court declined to hear the case in 2024.
McCrory has refused two plea deals that would have freed him in exchange for a guilty plea. He remains in prison after more than 38 years. No physical or forensic evidencePhysical evidence collected from a crime scene and analyzed scientifically to establish facts or reconstruct events; includes biological materials, trace evidence, and physical objects examined by forensic specialists., other than the recanted bite mark testimony, connects him to the crime.
Why Courts Still Allow It
The legal system’s deference to precedent creates a structural barrier to excluding discredited science. Courts look to prior decisions for guidance on admissibility. As Innocence Project attorney Dana Delger explained: “The notion is that the law shouldn’t really change very much, but that isn’t how science works at all.”
Science advances through new evidence and revised conclusions. The law advances through precedent. When prior courts admitted bite mark evidence, subsequent courts cite those decisions. The result is a feedback loop where yesterday’s bad science validates tomorrow’s bad convictions.
Professional organizations have also resisted reform. The ABFO and related associations, while acknowledging “past concerns,” have argued that the misidentifications occurred in the 1980s and 1990s and that current practitioners should not be judged by those standards. Critics note that the fundamental scientific objections, the lack of proven uniqueness, the unreliability of skin as a recording medium, and the inability of examiners to agree on basic questions, remain unchanged regardless of updated procedural guidelines. Such resistance to acknowledging fundamental flaws reflects what researchers call the curse of knowledgeA cognitive bias where knowing something makes it impossible to accurately imagine not knowing it, causing overestimation of how obvious that knowledge is to others.—the difficulty experts have in recognizing when their deeply held assumptions are wrong.
None of the forensic dentists who provided testimony later shown to be false have been held professionally accountable. As Chris Fabricant of the Innocence Project noted: “My sense of outrage is what gets me out of bed every day.”
The Path Forward
“Change in science” statutes offer one mechanism for relief. Six states, California, Connecticut, Michigan, Nevada, Texas, and Wyoming, have adopted such laws, creating pathways for people convicted on discredited evidence to have their cases reviewed.
But these statutes only address past convictions. They do not prevent future ones. Bite mark evidence remains admissible in most jurisdictions. The Innocence Project’s strategic litigation unit reports success in blocking its introduction in individual cases around the country, but there is no blanket prohibition.
“If you want to not only change what’s happening with bite marks, but to stop the next bite marks from getting into court,” Delger said, “that requires judges to be extremely skeptical and thorough when they are considering the admission of scientific evidence.”
The gap between what science knows and what the law permits continues to cost people their freedom. Every year that bite mark evidence remains admissible is another year that an innocent person could be convicted on testimony that four governmental bodies have declared worthless.
Keith Harward, who lost 33 years of his life to bite mark evidence, traveled to a conference of forensic dentists to confront them. Many were sympathetic, he said. But an old guard clings to the past. “How many times do you have to be told you’re wrong before you give it up?” he asked.
