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ABSTRACT
Forensic odontology has four primary applications. These applications include dental identification, bite mark assessment, dental age estimation, and standard of care. This article will focus on the history of forensic odontology in the United States as it relates to bite mark analysis. It will explore the DNA exoneration of Ray Krone who was sentenced to death for a murder he did not commit because of flawed bite mark analysis. The use of bite marks in the United States has had a turbulent history dating back over 300 years. It was first used during the Salem Witch trials in 1692, but it did not gain national attention until the State of Florida prosecuted serial killer Ted Bundy, and a key element of the state’s case was bite mark analysis. The Bundy case was the seminal case for the use of bite mark evidence in American courts. Over the next 30 years, numerous convictions based on bite marks cemented the evidence into the legal system as validated, legitimate, reliable, and admissible. Ray Krone’s conviction in 1992 was one of them. This article will evaluate the history of the questions surrounding bite mark analysis and comparison culminating in the recent National Institute of Standards and Technology (NIST) report and the basis for NIST’s conclusions as well as discussing the fate of bite mark analysis as an accepted forensic science discipline.
Introduction
The goal of this Article is to give the reader a historical overview of the use of bite mark evidence in the United States criminal legal system, providing a historical summary of the rise and use of this forensic discipline, as well as its decline. Historically the goal of bite mark analysis was accomplished by evaluating an injury bruise pattern in human skin and comparing that pattern to representations of a suspect’s dentition. The underpinning of such bite mark comparison rested on the ability of an expert to accurately distinguish between dentitions and associate a particular dentition to the injury bruise pattern. Milestone events that led to the use of this evidence in criminal courts in the United States will be discussed. Exonerations of those incarcerated or convicted on bite mark evidence will also be discussed along with scientific research that has called into question its validity as a forensic discipline.
The Rise of Bite Mark Analysis and a Turning Point Toward its Demise
Forensic bite mark analysis has been used in criminal cases in the United States since the 1600s. Today, its use has been determined to be unscientific. In order to understand the present status of bite mark evidence as a forensic identification science, it is helpful to understand and trace the history of the development of the use of bite mark evidence. As with many changes in our criminal legal system, forensic odontology as it relates to bite marks emerged as the result of landmark cases that established and shaped the evidence as a useful scientific tool within the greater forensic science legal community.
In the United States, the first reported use of bite mark evidence in a criminal case occurred nearly over 80 years before the American Revolution. On May 4, 1692, authorities arrested the Reverend George Burroughs in Salem, Massachusetts on false accusations of witchcraft, allegations spurred by some enemies of his former congregation.
At trial, the only physical evidence against Burroughs was bite mark evidence. The prosecution alleged Burroughs’s specter (a disembodied spirit) had appeared to several young women and had bitten them when they resisted the specter’s efforts to recruit them. During the trial proceedings, Burroughs’s “mouth was pried open and the prosecution compared his teeth with the teeth marks left on the bodies of several injured girls present in the courtroom.” The comparison was declared a match. At the time, judges readily accepted this presentation of bite mark evidence as a legitimate means to substantiate the allegations of the young women.
Burroughs continued to proclaim his innocence but was eventually executed by hanging on August 19, 1692. Two months later, the governor of Massachusetts called for an end to the witchcraft trials. He also prohibited the use of “spectral and intangible evidence” in criminal trials. Two decades later, Burroughs was declared innocent, and the colony of Massachusetts compensated his family for his wrongful conviction and execution.
Since Burroughs’s execution, bite mark evidence only surfaced in several criminal cases in the United States. It was not until almost 300 years later that the use of bite mark evidence in courtrooms exploded. The explosion can be attributed to a single case – the Florida trial of serial killer Theodore “Ted” Bundy who confessed to killing at least 28 female victims from at least seven different states during the mid to late 1970s. His was the first nationally publicized murder trial, covered by 250 reporters from five different continents. The extent of that coverage and the nature of the case against Bundy had profound effects on the acceptance and use of bite mark evidence in criminal cases.
In June of 1977, Bundy was facing murder charges in a Colorado court when he escaped from the courthouse. By January 1978, Bundy ended up in Florida where he acquired an apartment near Florida State University. On January 14, 1978, after a night of drinking, Bundy entered the Chi Omega Sorority House and attacked four sleeping young women by sneaking into the victims’ rooms and beating the victims unconscious. Two out of the four victims died from severe injuries inflicted by Bundy. Bundy had beaten one deceased victim with a club, raped her, sexually assaulted her with a metal hairspray can, and strangled her to death. The autopsy surgeon also discovered what he thought were bite marks on the victim’s buttocks and breasts. Bundy had also beaten the second deceased victim with a club and strangled her to death. She had a double bite mark on her left buttock with distinct marks where Bundy’s teeth had left bruises on her tissue. The two other victims, although beaten savagely, survived the attacks.
After leaving the Chi Omega Sorority House, Bundy broke into a nearby apartment and brutally attacked yet another Florida State University student, but she also survived. A few months later, in early February 1978, Bundy traveled to nearby Lake City, Florida. While there, he abducted, raped, and murdered a 12-year-old girl. He threw her body under a small shed 35 miles away.
A week after murdering the little girl, a police officer stopped and arrested Bundy because he was driving a stolen vehicle. At the time, the officer did not know he had just arrested one of the FBI’s most wanted men.
Before long, witnesses identified Bundy. He first stood trial for the Chi Omega Sorority House murders and the brutal assaults on the three surviving victims. The bite marks on the two deceased Chi Omega Sorority House victims were pivotal evidence against Bundy. Forensic odontologists matched bite marks from the deceased victims’ bodies to Bundy’s dental casts. He later stood trial and was convicted of the murder of the 12-year-old girl. Bundy received the death sentence for his crimes. While appealing, he would go on to confess to dozens of murders in gruesome detail. After he exhausted all his appeals, the State of Florida executed Bundy on January 24, 1989. The Bundy case was the functional equivalent of the moon landing for bite mark evidence.
The magnitude of Bundy’s crimes and the notoriety which the case attracted solidified bite mark evidence as a legitimate and valid forensic science. It sent a clear message to law enforcement in the United States and elsewhere that bite mark evidence could and should be used to establish identity of a perpetrator and obtain a conviction. After all, what could be more powerful evidence of criminal intent than a vicious bite mark on a victim?
The “undoing” of bite mark evidence as a valid “science,” would be years in the making. Although a case or study here or there occasionally challenged bite mark evidence as a “science,” it would not be until decades later when a murder at the CBS Lounge in west Phoenix, Arizona, a wrongful conviction for that murder, an overturned conviction, another wrongful conviction for that murder, a DNA exoneration, and trapping the true killer would pull on the loose thread of the bite mark sweater, causing it to unravel.
Hank Arredondo bought the CBS Lounge in mid-December 1991. It was Sunday, December 29, 1991, and Arredondo needed to let a carpenter in to the bar do some work. Arriving shortly after 8:00 a.m., Arredondo went to unlock the front door but found the door was already unlocked. He went inside and noticed several things out of place. In the men’s bathroom, Arredondo found employee Kim Ancona, a divorced mother of three who had worked at the bar about six months, deceased on the floor. She was naked, her clothes were strewn around the room, and her blood was all over the bathroom. Police found footprints on the bathroom floor and in the kitchen, where a knife was missing.
An autopsy revealed someone had stabbed Ancona eight times – twice in the back and six times in the neck. She had died around 2:00 a.m. The perpetrator had also bit Ancona’s breast and neck, leaving pattern injuries in her skin. Saliva collected from Ancona’s body came from someone with the most common blood type. Other DNA tests were inconclusive. There were no eyewitnesses or surveillance video.
The afternoon of the murder, police knocked on Ray Krone’s door. Ancona had told a friend that Krone, a regular customer at the bar, was going to help her close the bar the previous night. Krone had no previous criminal record, was top 10% in his high school class, a Sergeant in the United States Air Force who had been honorably discharged from the military, and a letter carrier for the United States Postal Service for seven years. Little did Krone know, opening the door to speak with police would set into motion a series of events that would cost him decades of his freedom.
Krone agreed to go to the Phoenix Police Department for questioning. He told police he knew Ancona, but only as an acquaintance. He played darts with her and talked to her at the bar, drove her to an afterhours Christmas party the week before, but nothing more. Before he left, police asked Krone to bite a piece of Styrofoam. ( one photo of Styrofoam bite) He did so without hesitation. Police then took him home.
Figure 1. Styrofoam impression from Ray Krone
After dropping Krone off at home, the lead investigator on the case took Krone’s Styrofoam bite mark sample back to the crime scene. When he got there, the investigator showed Krone’s bite mark to Dr. John Piakis, a local dentist who worked as the Forensic Odontologist for the Maricopa County Medical Examiner’s office who agreed to help the Phoenix Police Department on the case. Krone had noticeably crooked teeth and, in Dr. Piakis’s opinion, Krone’s sample was consistent with the mark on Ancona’s left breast. “Only someone with a snaggletooth, like Krone, could have made that mark”. And just like that, police thought they had their man, just a little more than 12 hours after the murder.
On December 31, 1991, just two days after the murder, police arrested Krone and charged him with Ancona’s murder, kidnapping, and sexual assault. Krone was infamously dubbed by the media as the “Snaggletooth Killer.” From then on, police focused only on evidence that led to Krone, disregarding leads that might point in other directions. Krone himself told his family he was not worried, it was all a mistake, and he would be released soon. “The state couldn’t convict me,” he said, “because I didn’t do it.” But he was wrong.
At his 1992 trial, Krone maintained his innocence, claiming to be asleep in his bed at the time of the crime. Krone had not been feeling well the night before Ancona’s murder. He was hungover from drinking heavily the day before and into the early morning. Instead of going out, Krone and his roommate did “basically nothing” all day, they sat around the house, ordered a pizza, and watched football on television. Krone went to his room about 10:00 p.m. He read for a while and then went to sleep.
Forensic odontologist experts for the prosecution, however, testified the bite marks found on Ancona’s body positively matched the impression that Krone had made on the Styrofoam. One, Dr. Raymond Rawson, an ABFO board-certified forensic odontologist testified and produced a video to explain his technique and how he arrived at his conclusion showing the positive “match” between Krone’s teeth and the bite marks on the victim. He testified, “Krone made the bite mark on Ancona’s left breast, which occurred at or near the time of death.” He also claimed bite mark comparison was more reliable than other forensic science disciplines, testifying “It’s not if bite mark evidence is as good as fingerprints, it’s if fingerprints are as good as bite marks!” And he told the jury, “A match is not 90% or 99% a match is 100% there is no other possibility.” If Krone made the bite mark to the exclusion of all others, it was irrefutable evidence that Krone’s alibi was fabricated and that he was guilty of murder. “There wasn’t a whole lot of forensic evidence,” Krone’s attorney said. “This was what you call a bite mark evidence case.”
Not surprisingly, given the damning bite mark evidence on the murder victim’s body, a jury convicted Krone and the trial judge sentenced him to die. At Krone’s sentencing hearing, the trial judge found aggravating circumstances:
The defendant committed the offense in an especially heinous, cruel or depraved manner.
Evidence of bite mark mutilation suggested debasement and perversion.
The murder was “so shocking and repugnant that it stands out from the norm of first-degree murders.”
(Judge Jeffrey Hotham in his November 20, 1992, Special Verdict imposing the death penalty on Ray Krone.) Upon reading the sentence, the audience in the packed courtroom burst into applause.
In 1996, Krone won a new trial on appeal, but was convicted again. And, just like the first trial, the predominant evidence against him was the testimony regarding the bite mark evidence. This time, however, a different trial judge spared him the death penalty and sentenced him to life in prison, expressing doubts about whether Krone was Ancona’s true killer. Far from the statements of the first trial judge, the second trial judge commented, “This is one of those cases which will haunt me for the rest of my life, wondering whether I did the right thing.” (Judge James McDougall in his December 9, 1996, Special Verdict.)
In 2002, after Krone had served more than a decade in prison, some of it on death row, DNA testing finally proved his innocence and identified Ancona’s true killer. DNA testing conducted on the saliva on Ancona’s clothing excluded Krone as the source. The unknown genetic profile from the saliva was entered into the national DNA database and produced a hit to a man named Kenneth Phillips. Phillips was incarcerated on an unrelated sex crime and, although he had lived a short distance from the bar where Ancona worked, he had never been considered a suspect in her murder. What’s more, Phillips did not have crooked teeth. The claim that the bite mark on Ancona’s body could have only been produced by a person with a snaggletooth was patently untrue. (See dentition of Krone and Phillips side by side).
Figure 2. Dental Model from Ray Krone
Figure 3. Dental model from Ken Phillips
On April 8, 2002, Krone was released from prison and, a month later, prosecutors dismissed all charges against him. Krone was the 100th former death row inmate freed on grounds of innocence since the reinstatement of capital punishment in the United States in 1976. He was the 12th death row inmate whose innocence was proven through DNA. Murder and sexual assault charges were brought against Philips, and he is currently serving a term of 53 years to life in prison for the crimes.
The Krone case has been cited in numerous legal and scientific contexts as a pivotal moment in which the reliability of bite mark evidence as a forensic science has been undermined.
Validity and Reliability of Bite Mark Analysis
Ray Krone’s case was presented in detail to the Odontology section at the 2004 American Academy of Forensic Science (AAFS) meeting held in Dallas, Texas. The AAFS is an international organization composed of members from various forensic science disciplines, that “provides leadership to advance science and its application to the legal system.” Its meetings are designed to educate attendees about emerging issues in forensic science, including bringing to light its failures. The Krone case spotlighted a real problem with the forensic “science” area of bite mark comparison. Unlike some other cases involving bite mark evidence but where there was other compelling evidence of guilt, there was no dispute in Krone’s case that he was innocent and that an error regarding the interpretation of the bite mark evidence occurred. DNA, fingerprints, and other evidence, including incriminating statements by the true perpetrator, conclusively identified the real killer and exonerated Krone.
Krone’s case had also been studied extensively by the American Board of Forensic Odontology (ABFO), many members of whom are also involved in AAFS, to determine how and why the experts in Krone’s case got it so wrong. The ABFO was founded to “establish, enhance, and revise as necessary, standards of qualifications for those who practice forensic odontology” as well as certify odontologists in the practice of forensic odontology. Because of the Krone case, the ABFO changed its guidelines to limit the use of certainty statements, such as were used by Dr. Rawson in Krone’s case.
After Ray Krone’s exoneration, the greater scientific community began asking questions about the scientific validity of bite mark evidence. Could forensic dentists reliably and accurately identify whether a patterned injury is a human bite mark? If so, could they reliably and accurately distinguish between patterned injuries made by adults versus those made by children? And, if so, was there any scientific support for the contention that a well-trained forensic odontologist could reliably and accurately exclude or include a particular individual from having made the bite mark?
In 2009, the National Academy of Sciences (NAS), a private nonprofit organization that provides independent and objective advice to the United States on issues involving science and technology, issued a report on forensic science raising questions relating to several forensic science disciplines. One of those was bite mark evidence. The NAS report concluded: “More research is needed to confirm the fundamental basis for the science of bite mark comparison. [T]he scientific basis is insufficient to conclude that bite mark comparisons can result in a conclusive match.” (Nat’l Research Council, Nat’l Acad. of Scis., Strengthening Forensic Science in the United States: A Path Forward 175 (2009).) The inquiry into whether bite mark evidence was a legitimate “science” did not begin, nor did it end there.
Experts working in the area of bite mark analysis have called for more rigorous research since 1960. A 2016 study found that experts could not agree on the diagnosis of a bite mark. (Page et al. 2013, Freeman & Pretty 2015, Reesu & Brown 2016). Further, experts could not even agree with themselves when they reviewed the same case eight weeks later. Similar results had been obtained in 1975, 1998, and 2001, but no real attention had been given to these studies. What these years of research proved, however, was that bite mark experts were not using a reliable or consistent technique to analyze bite marks and, even if they did so, they could not reach reliable and consistent results. In 2016, the Texas Forensic Science Commission recommended a moratorium on the admission of bite mark testimony. It stated: “We concluded that bite marks should not be admitted in criminal cases at this point. We feel it does not meet the standards of forensic science.”
In 2019, a workshop on human bite marks concluded that bite marks were not specific to an individual, like fingerprints. The workshop concluded it was “highly unlikely” teeth had characteristics that could be used to identify individuals. This openly contradicted the claims made by forensic odontologists working in the area that bite marks were unique to the individual and could be compared in the same way fingerprints or DNA were used to link suspects to a crime. There simply is not enough detail available from an individual’s teeth to conclude that every dentition is unique, and that the uniqueness transfers a corresponding unique pattern to skin and tissue during a biting event.
Then, in March of 2023, the National Institute of Standards and Technology (NIST), a United States governmental organization involved in science and technology, released a report titled “Bitemark Analysis: A NIST Scientific Foundation Review”. They concluded that “forensic bite mark analysis lacks a sufficient scientific foundation” altogether. The report identified the following key assumptions of bite mark analysis that are not supported by the data:
KEY TAKEAWAY #1.1: Forensic bite mark analysis lacks a sufficient scientific foundation because the three key premises of the field are not supported by the data. First, human anterior dental patterns have not been shown to be unique at the individual level. Second, those patterns are not accurately transferred to human skin consistently. Third, it has not been shown that defining characteristics of those patterns can be accurately analyzed to exclude or not exclude individuals as the source of a bite mark.
KEY TAKEAWAY #2.1: The entire human dentition is not represented in a bite mark. Bite mark patterns typically only represent the anterior teeth and thus not the full possible dentition of an individual, limiting the amount of information available for an analysis.
KEY TAKEAWAY #4.1: There is a lack of research into population frequencies, specific identifying characteristics, and measurements that support the notion that human anterior dental patterns as reflected in bite marks are unique to individuals.
KEY TAKEAWAY #4.2: Accurate transference of an anterior dentition pattern in the form of a bite mark on human skin can be limited by distortions caused by skin elasticity, unevenness of the biting surface, location of the bite, and movement of the biter and/or victim during the biting event.
KEY TAKEAWAY #4.3: Comparisons between bite mark patterns made on skin, for example multiple bite marks from the same individual on the same victim, have shown that there exists intra-individual variation in bite mark morphology on the human body such that bite marks from the same biter may not appear consistent.
KEY TAKEAWAY #4.4: Bite marks in cadaver-based research studies are representative of highly controlled experimental conditions and these results may overestimate the accuracy of analysis methods. Bite marks in actual cases, where controlled conditions are not present, are prone to higher levels of inaccuracy.
KEY TAKEAWAY #4.5: As reflected in research studies to date, bite mark examiners may not agree on the interpretation of a specific bite mark, including whether the injury is a bite mark, the features present, and the exclusion or non-exclusion of potential biters.
(NIST Interagency Report 2 NIST IR 8352-DRAFT Bitemark Analysis: 5 A NIST Scientific Foundation Review.)
What the history of bite mark evidence shows is that even highly qualified forensic odontologists cannot reliably and accurately identify whether a patterned injury is a human bite mark or let alone whether a bite mark was made by a particular person. There simply is no credible scientific data which supports an expert opinion that a particular bite mark can be associated to a particular perpetrator’s dentition. Testimony describing a human dentition as “like a fingerprint” or incorporating similar analogies lack fundamental scientific support. Similarly, there is no scientific basis for assigning probability or statistical weight to an association between a dentition and suspected bite mark, regardless of whether such probability or weight is expressed numerically (e.g., 1 in a million) or using some form of verbal scale (e.g., highly likely/unlikely). Though these types of claims were once thought to be acceptable, were sanctioned by the ABFO, and have been admitted into evidence in criminal cases, it is now clear they have no place in our criminal justice system. Not only do they lack any credible scientific basis, but they have cost innocent people years of their lives, if not their actual life. The use of such evidence is scientifically and morally unacceptable in our criminal legal system.
Conclusion
Reverend George Burroughs in 1692 was the first person in the United States to be executed based upon bite mark evidence. Ironically, Burroughs was also the first bite mark exoneration in the United States. Ray Krone was convicted of murder in 1992 and, like Burroughs, his guilt was based on bite mark evidence and again, like Burroughs, he was also exonerated. After 300 years of using of bite mark evidence in criminal cases, its legitimacy has been irreparably undermined by the general scientific community largely due to DNA such as in Krone’s case.
Additional information
Notes on contributors
Alissa Bjerkhoel
Alissa Bjerkhoel has been an attorney with the California Innocence Project since 2008. She coordinates all active case litigation, serves as the in-house DNA legal expert, directs and supervises clinical student casework, petitions for release of innocent clients, and helps draft new laws. She is a Fellow of the American Academy of Forensic Sciences, is one of the five members of the National Innocence Network’s Complex DNA Working Group, and she serves on the Innocence Network Executive Board. Alissa has been instrumental in a number of exonerations and has been featured on local and national television shows, podcasts, and was portrayed in the feature film “Brian Banks.” She has received a number of awards including “Young Attorney of the Year,” “Post-Conviction Lawyer of the Year,” “Attorney of the Year,” and was recently recognized by the San Diego Union-Tribune as one of the “Phenomenal San Diego Women in Law And Public Safety.”
Hon Christopher J. Plourd
Hon Christopher J. Plourd, Judge Superior Court of Imperial County California, is a fellow of the American Academy of Forensic Sciences, a member of ASTM International E-30 Committee on Forensic Science, the American Association for the Advancement of Science, and the American Society of Forensic Odontology. Judge Plourd completed term on the national Forensic Science Standards Board in 2019. Currently Judge Plourd is a voting member to the Organization of Scientific Area Committee (OSAC) Forensic Science Toxicology scientific subcommittee.