The Science of Bite Mark Evidence

The use of bite mark evidence in the court room has been a widely accepted practice for decades. The science seems to make sense when looking at the surface; however, dig a little deeper and you will see the flaws behind the science of bite mark evidence making many question the validity of the practice, and why it is still admissible in court.

Bite marks are typically seen in cases of homicide, sexual assault, and child abuse. When an assailant has been arrested or charged, courts will sometimes use a forensic odontologist as an expert to prove that the bite mark found on the victim matches the bite mark of the assailant. There are numerous techniques used to obtain bite mark evidence from the human body including: photographs, dental casts, clear overlays, computer enhancement, electron microscopy and swabbing for serology or DNA. The techniques used are not the issue – rather the issue is whether human skin is a reliable surface to collect data.

The answer is no. In fact, human skin has a great degree of elasticity making it one of the most unreliable surfaces to collect data from. Its ability to change size and shape quickly makes it incredibly difficult to measure a mark found on the skin. For example, if Jane were to be assaulted by John, and John bit Jane on the arm at 1:00 a.m. but Jane did not call the police until 9:00 a.m., the bite mark is going to look very different at 9:00 a.m. than it would have at 1:00 a.m. when the incident occurred. This is because of the swelling. The swelling causes the bite mark to become distorted which can drastically change the size and shape of the bite mark potentially causing the wrong person to be convicted of the crime.

Although bite mark evidence has put away many people who have indeed committed specific acts, it has also caused numerous innocent people to serve a prison sentence for a crime they did not commit. In 2006 Willie Jackson was accused of rape in Louisiana. There were several factors that connected Willie Jackson’s brother to the crime, including a sweater that had his brother’s name on it that was similar to the one described by the victim, Willie Jackson’s mother drove a car that fit the description of the car driven by the perpetrator, and the bartender testified that he saw Jackson’s brother, not Willie Jackson himself in the same exact bar as the victim the night of the crime. Despite the clear connection between Willie Jackson’s brother and the crime, the prosecution used a forensic odontologist who testified that the bite mark on the victim matched Willie Jackson’s teeth. The brother confessed to the crime six days later but was not charged. Sixteen years later, Willie Jackson was released from prison based on the finding that the DNA on the victim did not match Willie Jackson, rather it matched his brother who was already serving a life sentence for an unrelated rape.

Willie’s case is just one of many where the prosecution relied on the use of a practice that is founded on unreliable science. DNA testing has revealed the flaws in using bite mark evidence, yet courts still proceed to allow such evidence to be admitted despite its unreliability.

Erin Powers is a Law Clerk at Ambrose Law Firm, PLLC in Minneapolis, MN. Erin is a 2L at the University of St. Thomas School of Law. She graduated magna cum laude from the University of Minnesota. Erin also volunteered for the Center for Integrity in Forensic Science. Criminal Defense Lawyers Woodbury MN; Criminal Attorneys Minnesota; and Criminal Appeals Attorney MN.

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