Bite Mark Analysis in Forensic Odontology: Basics Guide

A bite mark is a patterned injury left when teeth press into skin or food, and in violent crimes it can be the only physical link between attacker and victim. Bite mark analysis is the forensic odontology discipline that documents these marks and compares them with the teeth of suspects. Because no two people share the same combination of tooth size, alignment, rotations, chips and wear, a bite mark can, in principle, include or exclude a suspect.

In practice, bite mark analysis is one of the most debated areas of forensic science. Skin stretches, swells and heals, so the mark is always a distorted copy of the teeth. The US National Academy of Sciences (2009) and PCAST (2016) reports concluded the science needs much stronger validation, and several courts now limit such testimony. Modern practice therefore emphasises careful documentation, DNA recovery, and conservative conclusions.

Key Concepts

• Class characteristics: features shared by groups, such as the U-shape of the dental arch.
• Individual characteristics: unique traits like a rotated tooth, a chipped edge or a gap.
• ABFO guidelines: the American Board of Forensic Odontology's standards for photographing (with an ABFO No. 2 scale), swabbing and describing bite marks.
• Double-swab technique: a moistened swab followed by a dry swab to recover the biter's saliva DNA — often more valuable than the pattern itself.
• Distortion: the stretching of skin that changes the mark's size and shape relative to the teeth.
• Overlay comparison: superimposing an outline of a suspect's teeth over a life-size photograph of the mark.

How It Works

1. Photograph the mark immediately with an ABFO scale at right angles, plus close-ups.
2. Swab the area twice (wet then dry) for saliva DNA before touching the mark further.
3. Take impressions or 3D scans if the mark has depth.
4. Record the victim's own dentition to rule out self-inflicted marks.
5. Make dental casts of each suspect and compare with measured overlays.
6. Conclude conservatively: exclusion, inconclusive, or — only with strong correspondence — a qualified inclusion.

Worked Example

A bite mark on a forearm is photographed with a scale. Step 1: distance between the two canine marks = 33 mm. Step 2: the suspect's intercanine width on the dental cast = 32.5 mm. Step 3: difference = 33 − 32.5 = 0.5 mm, within expected skin distortion. Step 4: a second suspect measures 38 mm — a 5 mm gap skin cannot explain, so suspect 2 is excluded. The analysis narrows the field but does not uniquely prove suspect 1 is the biter.

Common Misconceptions

• Bite marks are as reliable as fingerprints. Fingerprints sit on a stable surface; bite marks sit on living, elastic, healing skin.
• Every bite mark identifies the biter. Often the only safe conclusion is exclusion — ruling suspects out, which is still extremely useful.
• Dentists can match a bite to one person in the world. No method can do that; responsible experts report degrees of correspondence.

Real-World Applications

• Assault and homicide investigations where the attacker bit the victim during a struggle.
• Child abuse cases, where bite marks may be the clearest evidence of assault.
• Reviewing old convictions where overstated bite mark testimony has been overturned.
• Food-borne bite evidence, such as cheese or fruit bitten at a crime scene, which preserves detail better than skin.

Bite mark analysis demands both dental skill and scientific honesty. Its greatest strengths are meticulous documentation, saliva DNA recovery and the power to exclude the innocent. Used with restraint and full disclosure of its limits, it remains a legitimate — if carefully bounded — forensic tool.