Say Cheese! Teeth and Forensics

Author: Ellie Livitsanou

Editors: Shamsia Ahmed and Kira Tian

Artist: Abhinaya Vijayanand

Forensic Science has been used for decades by experts to investigate crime and prosecute people. There are four main types of judicial branches experts rely on that relate to the human body: Time of Death, Hair, Fingerprints, and Teeth Marks. Some cases that rely on Teeth Marks, where the suspect has been locked up (or put on death row) for serious crimes. But what if these “bad guys’’ aren’t bad? There have been two reports made by experts that question the reliability of Teeth Marks in forensics. Before we get into the validity of Teeth Marks, first let’s understand how Teeth Marks are used.

Teeth Marks had a rather unusual entry into U.S. court — the victim wasn't human! The victim was a portion of delicious, yellow food that is often paired with crackers. Can you guess what it is? CHEESE! Yep, you read right, cheese. This happened in a grocery store in the 1950s. The store was robbed, and the robber took a bite of cheese. The detective on the case had an idea: if they could match the teeth marks on the cheese to an actual set of teeth, they could find out who had done it. They had a suspect already: an alcoholic that lived in the area. So the detectives gave the suspect another piece of cheese to bite into. The detective then made a cast of both marks, compared them, and voila! They matched, and they had caught their robber.

To this day, professional detectives still use similar methods. First, they take a photograph of the victim’s area of skin where there is a mark. Then, if there’s a suspect, a so-called “forensic dentist’’ makes a mold of their teeth and then uses it to bite into something, commonly pigskin or the skin of a deceased person. They proceed to take a photo of this new mark and compare it to the picture on the victim’s body. If they find it very similar, they consider the person guilty. One of the most well-known cases is one of a serial killer named Ted Bundy. They found two bite marks on one of his victims and linked them to Bundy, which secured his conviction.

The trouble is that not all cases with teeth marks are as clean as Ted Bundy’s. Barry Fisher, an expert that has 22 years of experience in a crime lab (where police send the evidence to experts in Forensic Science), has some concerns about using teeth marks as evidence. He says that the problem with skin is that skin is not elastic. The skin bounces back when something bites it, which means that the mark in the photograph they take isn’t an exact representation of the teeth’s shape.

He also mentions that you cannot reliably tell people’s teeth apart. A 2010 study looked at 100s of sets of teeth and found that ‘’Uniqueness cannot be demonstrated’’. Later research that looked at 1000s of sets of 3D scanned teeth confirmed this, stating that “they don’t vary that widely from person to person’’. Another problem with this method is that sometimes experts cannot even tell if the mark is from human teeth.

After a six month investigation, the Texas Forensic Science Commission recommended a halt on the use of bite mark analysis until the science behind it improves. Some have lost all hope for bite mark analysis. The president’s council wrote: “bitemark analysis is so bad it may not be salvageable”.

Would you trust bite mark evidence?

Citation

2016 President’s Council of Advisors on Science and Technology reports on forensic

science

Review paper on bite mark analysis Clement et al, “Is current bite mark analysis a

misnomer?” Strengthening Forensic Science in the United States: a Path Forward.

National Academies Press, 2009.

Vs, Science. “Forensic Science: Science Vs.” Gimlet, Gimlet, 15 Apr. 2019,

gimletmedia.com/shows/science-vs/emhwgd/forensic-science.

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