Bite Marks in Forensic Odontology: Types and Analysis

A bruise shaped like a horseshoe on a victim’s forearm. A chunk missing from an apple left behind on a kitchen counter. Torn skin on a child’s cheek that nobody can quite explain. All of these can qualify as bite marks, and in forensic odontology, they carry more evidentiary weight than most people realise. A bite mark isn’t just an injury – it’s a signature left by someone’s dentition, and reading that signature correctly can make or break a criminal case.

What exactly counts as a bite mark 🔗

The American Board of Forensic Odontology defines a bitemark as a physical alteration or representative pattern recorded in a medium, caused by the contact of teeth belonging to a human or an animal. In plainer terms, a bite mark is what’s left behind when teeth, sometimes along with other oral structures like the tongue or lips, press into skin or an object and leave behind a recognisable dental pattern.

These marks don’t only appear on human skin. Forensic odontologists also encounter bite marks on food items, wax, chewing gum, and even musical instruments, wherever teeth have made physical contact and left a trace of their shape behind.

Classifying bite marks: human, animal, criminal, and non-criminal 🔗

The first job for any forensic odontologist examining a suspicious mark is deciding whether it’s human or non-human in origin. Animal bites, especially from dogs, tend to leave narrower, more triangular patterns with deeper puncture points compared to the broader, more rounded arch of human teeth. Getting this distinction right matters, because it determines the entire direction of the investigation.

Once a mark is confirmed as human, it’s further sorted by intent. Non-criminal bite marks might occur accidentally, during sports, roughhousing, or even self-inflicted injury. Criminal bite marks are the ones investigators focus on, and these are split further:

Offensive and defensive bites 🔗

An offensive bite mark is one the assailant inflicts on the victim, often seen in cases of assault, abuse, or sexual violence. A defensive bite mark is the reverse: a mark the victim leaves on the attacker while fighting back. Both carry forensic value, but defensive marks are particularly useful because they can appear on a suspect’s body, giving investigators a direct physical link between attacker and victim.

The seven types of bite mark injuries 🔗

Bite marks aren’t a single, uniform kind of injury. Depending on the force applied and how the tissue responds, a bite can present in seven distinct ways:

Haemorrhage – a small, localised bleeding spot where a single tooth has pierced the skin’s surface.

Incision – a neat puncture or tear caused when a sharper tooth edge cuts cleanly through skin.

Laceration – a puncture of the skin resulting from tooth pressure combined with tearing force.

Contusion – the most commonly seen pattern, where blood vessels rupture under the skin’s surface and produce a visible bruise without breaking the skin.

Abrasion – a superficial, non-damaging mark left when teeth scrape across the skin without breaking it.

Artefact – a more severe injury where a piece of the body has actually been bitten off.

Avulsion – the removal of a layer of skin caused by the bite.

Recognising which of these categories a mark falls into helps investigators judge the amount of force used and, in violent crime cases, the intent behind the attack.

How a bite mark actually forms 🔗

Three mechanisms are chiefly responsible for how a bite mark takes shape: tooth pressure, tongue pressure, and tooth scrape. Tooth pressure is the direct force of the teeth pressing into tissue. Tongue pressure adds an inward suction-like force that can distort the pattern further. Tooth scrape happens when teeth drag across the surface rather than clamping straight down, producing streaked or elongated marks rather than clean impressions.

How severe the resulting mark looks depends heavily on how much the jaw moved during the bite and how long the pressure was sustained. A quick, controlled bite looks very different from one where the jaw twisted or the victim struggled, which is one reason no two bite marks, even from the same person, ever look identical.

Grading the impression 🔗

Forensic odontologists also grade bite marks by how clearly the dental pattern comes through. Marks fall into four broad categories: clearly defined, where individual tooth marks are sharp and distinct; obviously defined, where the overall arch is visible but some detail is lost; quite noticeable, where only a general bite pattern remains; and lacerated, where tearing has destroyed most of the fine detail needed for a precise comparison.

Reading the teeth: dental characteristics used for identification 🔗

Human dentition is remarkably individual. Research into using bite marks for even gender determination notes that the distinctiveness of human teeth allows forensic odontologists to reach strong conclusions in personal identification cases, even though bite marks can be distorted by the elasticity of skin, the pressure applied, and the angle at which the jaws met the surface.

Class characteristics 🔗

Class characteristics are the features shared by an entire type of tooth. Central and lateral incisors, for instance, tend to leave fairly uniform, blade-like marks, while canines are cone-shaped and leave sharper, more pointed impressions. These broad features help confirm that a mark is indeed a bite and rule out other kinds of patterned injuries, such as those from blunt objects or clasps.

Individual characteristics 🔗

What actually narrows a bite mark down to one specific person are individual characteristics – the quirks that deviate from the standard class pattern. These include rotated teeth, buccal or lingual version (teeth angled outward or inward), fractures, missing or extra teeth, drifting, and wear patterns from attrition, abrasion, or erosion. Dental restorations, old injuries, and even certain biologic conditions affecting the teeth also leave detectable traces. Because every mouth accumulates its own combination of these quirks over a lifetime, the old forensic principle that “no two mouths are alike” gives bite marks genuine value as an identification tool, standing alongside more familiar methods like fingerprinting.

Alongside the physical pattern, odontologists routinely swab the bite site for saliva. Investigators are advised that saliva deposited by the biter on the victim’s skin should be recovered since it can carry DNA and other biological markers, and a comparison buccal swab is typically taken from any suspect for matching. Newer research is even exploring whether the specific mix of bacteria naturally present in saliva can help strengthen the link between a bite mark and its source when paired with conventional DNA profiling.

Where bite marks turn up and how they’re documented 🔗

Bite marks are most frequently encountered in homicides, sexual assaults, child abuse cases, physical altercations, and abduction cases. On the body, they commonly appear on the face, neck, arms, ears, breasts, legs, shoulders, buttocks, waist, and genitals. Outside the body, offenders sometimes leave unintentional bite marks on food items at a crime scene, which can be just as valuable as skin impressions since they preserve tooth patterns without the distortion that skin introduces.

Because bite marks change and fade quickly, documentation has to happen fast and precisely. Standard practice, following ABFO guidelines for evidence collection, calls for photographing the mark from multiple angles, always with a scale or ruler placed alongside it so the exact size can be reconstructed later. Photographs are typically taken with and without flash, in colour as well as black and white, and impressions or casts may be made if the injury has enough surface detail. Any resemblance an odontologist notices between a mark and a known set of teeth is expected to be reported without delay, since bite marks are perishable evidence that won’t wait for a convenient moment.

Why bite mark analysis is harder than it looks 🔗

Despite its potential, bite mark analysis is one of the more contested areas of forensic science. Skin is elastic and curved, not flat like paper, so the same set of teeth can produce noticeably different marks depending on where on the body the bite lands, how much the victim moved, and how much time has passed since the injury occurred. A bite on the forearm can look nothing like a bite on the shoulder from the very same person.

This variability has real legal consequences. The Innocence Project has documented multiple wrongful convictions that were built largely or entirely on bite mark testimony, cases where odontologists later admitted their original conclusions could not be scientifically supported. A 2009 National Academy of Sciences report specifically flagged bite mark comparison for its high error rates, and the American Board of Forensic Odontology has since revised its own standards to stop experts from claiming a bite mark can be unconditionally linked to one specific person’s teeth.

None of this means bite mark evidence is useless. It remains genuinely valuable for excluding suspects, for guiding an investigation in its early stages, and for corroborating other evidence like DNA. But it works best as one piece of a larger puzzle rather than the sole basis for a conviction, which is exactly why modern forensic odontology leans more heavily on saliva-based DNA analysis alongside the traditional visual comparison of tooth patterns.

What do you think? Given how much a bite mark’s appearance can change based on body location and time elapsed, should courts treat it purely as supporting evidence rather than standalone proof? And as DNA and microbiome analysis keep improving, do you think the visual comparison of tooth patterns will eventually become secondary to biological testing in bite mark cases?

References

1. https://nvlpubs.nist.gov/nistpubs/ir/2023/NIST.IR.8352.pdf
2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6198570/
3. https://www.ojp.gov/ncjrs/virtual-library/abstracts/human-bitemarks-recovery-forensic-evidence-suspects
4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11294684/
5. https://www.dentalcare.com/en-us/ce-courses/ce401/bite-marks
6. https://innocenceproject.org/news/why-bite-mark-evidence-should-never-be-used-in-criminal-trials/
7. https://deathpenaltyinfo.org/policy-issues/policy/junk-science/bite-mark-comparison