Lip, Ear and Bite Marks: Cheiloscopy and Forensic Odontology

The lip's free border (the vermilion zone) carries a pattern of grooves called sulci labiorum. LeMoyne Snyder's 1950 textbook Homicide Investigation was the first English-language work to argue these grooves could be used for identification, building on Locard's 1932 recommendation that lip prints be used in personal identification. By the 1970s the Japanese researchers Suzuki and Tsuchihashi had surveyed enough lip-print samples to propose the five-type classification still used today.

A few facts worth holding clearly. Lip prints are stable across adult life unless trauma or disease (cheilitis, herpes labialis scarring) alters the surface. The pattern is laid down during the third intrauterine month. Identical twins show similar but not identical patterns, which is the strongest argument the field has for some discriminating power. Population studies from Indian samples (a much-cited 2014 Chandigarh study; AIIMS Delhi work in 2019) report Type II and Type III dominate among north Indians, with regional variation that has been used to argue for population-specific reference databases.

The Indian SFSL practical reality is more modest. Lip-print evidence appears in casework as one circumstantial strand alongside DNA, fingerprints and CCTV. No published Indian conviction rests on cheiloscopy alone, and the cases that get cited (Karnataka glass-marked-with-lipstick robberies; a few Mumbai sexual-assault matters) all had corroborating physical evidence. Cross-link to Forensic Photography for the documentation grade that lip-print photographs need.

The collection workflow is substrate-dependent. Most lip prints recovered in Indian casework come from drinking glasses, tea cups, cigarette butts, bottle rims, envelope seals and the occasional kissed letter. Each surface needs a different development method.

1. Recognition and on-scene photography
   Scan glassware and cup rims under oblique light or a 365 nm UV torch; lipstick-bearing prints often fluoresce weakly. Photograph in situ with the ABFO scale before any chemical step. The on-scene photograph is the only record of the print's original substrate orientation.
2. Direct visible prints (with lipstick)
   If pigment is already visible, the print is photographed with overview, mid-range and close-up shots (three-shot rule), then the substrate is packaged whole. No development is needed. Glass is wrapped in tissue and boxed; cigarette butts go into paper envelopes, never plastic.
3. Latent prints (no visible lipstick)
   On non-porous surfaces (glass, ceramic, polished metal), apply magnetic powder with a magnetic wand, working from the outer edge inward. Aluminium powder is the second-choice option. Both raise the lip print as a dustable image that is then photographed and lifted with adhesive tape on a contrasting card.
4. Dark or smudged lipstick on dark substrates
   Use aluminium powder for high contrast, or switch to small-particle reagent for damp surfaces. Lysochromes (Sudan III, Oil Red O) selectively stain the fatty component of lipstick and are sometimes used in lab development, not at the scene.
5. Lifting and packaging the lift
   Adhesive tape lift onto a backing card of contrasting colour (black card for white powder, white card for black powder). Label with scene exhibit number, location of recovery, lifter's name and date. The lift is then re-photographed under controlled lab conditions before any comparison work begins.
6. Reference lip prints from the suspect
   Apply unflavoured lipstick or lip cosmetic to the suspect's vermilion, blot once on filter paper, then take three full-lip impressions on glass or photo paper. Repeat for upper and lower lips separately. The reference set goes to the lab with the lifted print for comparison.

The Indian SFSL anchor here is the standard kit issued to state SOCO teams: magnetic powder, aluminium powder, ABFO scale, an envelope set for cigarette butts and a small lip-print reference pad. State FSLs in Gandhinagar (NFSU campus), Hyderabad and Madhuban have all published kit lists that include these items as routine.

The earprint is the rarest of the three. The external ear is anatomically complex (helix, antihelix, scapha, triangular fossa, tragus, antitragus, lobe) and the cartilage is firm enough that when a person presses an ear against a door or window during eavesdropping or forced entry, an oily latent print transfers in a way that captures most of those features.

Alfred Iannarelli proposed a 12-measurement system in 1989 based on a sample of around 10,000 ears. The measurements are pair-wise distances between the seven anatomical landmarks shown above. He argued the combined measurement set could discriminate at near-individual level. The trouble is that the sample was self-selected, the measurement protocol depended on operator skill, and reproducibility studies in the 2000s (the European FearID project, finished 2006) found inter-examiner agreement of only around 90% on the most discriminating measurements.

Indian SFSL casework with earprints is rare. The scenarios where it has been attempted include burglary cases where the suspect pressed an ear to a glass door, and one widely-cited Maharashtra case where a kidnapping suspect's ear had imprinted on a bound victim's clothing. In both, the earprint was offered alongside fingerprint and DNA evidence and was not the deciding strand. Otoscopy is retained as a teaching unit in Indian forensic-science courses, but the working level of mastery expected is landmark recognition rather than full identification math.

Bite marks are the most common of the three impression types in violent-crime casework, especially in sexual assault, child abuse and homicide. A bite mark is a patterned injury where the dental arch indents skin, food, chewing gum, a cigarette filter or similar deformable substrate. The forensic odontologist works from the photographed pattern back to a possible source dentition.

The on-scene collection workflow has been stable for two decades.

• Photograph first, in colour and with the ABFO No. 2 scale placed at 90° to the long axis of the camera lens, on the same plane as the bite. Take overview, mid-range and close-up exposures. Repeat under UV (365 nm) and IR if the bite is on light skin where bruising may be subdermal. Time-series photographs over 48 to 72 hours capture the bruise's progression, which can reveal pattern detail invisible at first.
• Swab the bite for salivary DNA before any other step that might wash it. Use the double-swab technique: first swab moistened with sterile saline to lift cellular material, second dry swab to absorb residual moisture. Package each swab separately in a paper envelope, air-dry, refrigerate, and forward to the DNA division. This is now the highest-value piece of evidence the bite produces, and almost every reported Indian SFSL bite-mark case has rested on the salivary DNA hit, not on the pattern comparison.
• Cast the bite if the surface is firm enough. Polyvinyl siloxane impression material (the same dental impression silicone used in clinical odontology) is layered over the bite once the swab is taken and the photographs are made. The set cast is a permanent three-dimensional record of the indentation. Skin is rarely firm enough for a usable cast; bite marks on chewing gum, fruit, cheese and chocolate cast well and are the cases where the cast is the primary exhibit.
• Reference dentition from the suspect. A clinical dentist takes upper and lower alginate impressions of the suspect's dental arches, plus a wax bite registration that captures occlusion. The casts are forwarded to the FSL odontology division for comparison.

A practical distinction worth holding cleanly: a bite on the victim is the suspect's dentition (offensive bite, often during an attack); a bite on the perpetrator is the victim's dentition (defensive bite, often during resistance). Both are documented identically. The investigative significance differs.

The American Board of Forensic Odontology published a scoring scale in 1995, updated several times since, that asks the examiner to grade the degree of similarity between the bite pattern and the suspect's dentition on a graduated scale (from "exclusion" through "inconclusive" to "the biter").

The 2009 National Academy of Sciences report Strengthening Forensic Science in the United States was the inflection point. Its bite-mark chapter concluded that "the scientific basis is insufficient to conclude that bite-mark comparisons can result in a conclusive match." The 2016 PCAST report repeated the finding more bluntly. Several US convictions that had rested on bite-mark testimony alone were vacated on DNA review, and a working group of US odontologists publicly walked back the uniqueness claim in 2018.

The Indian appellate response has tracked the international shift without ever fully embracing it. In Mohd. Aman v State of Rajasthan (1997), the Supreme Court of India addressed the reliability of forensic impression evidence and stressed that such testimony is corroborative, not the primary identification. The judgment is cited when forensic pattern-evidence admissibility is in dispute. The SFSL practice that has emerged in Gujarat, Maharashtra and Tamil Nadu is conservative: photograph, swab for DNA, document, report patterns as "consistent with" or "inconsistent with" the suspect's dentition, and never claim individual-source identification on pattern alone. Cross-link to Chain of Custody because every bite-mark swab fails in court the same way every other DNA swab fails, on a broken custody chain.

The following questions cover the three impression types, standard development and lifting methods, and the current scientific position on uniqueness.

• Name the five Suzuki-Tsuchihashi types and draw a representative pattern for each. Straightforward recall; the patterns are simple to sketch.
• Walk through the bite-mark collection sequence in order. Photograph (with ABFO scale at 90°), swab for DNA (double-swab), cast if substrate allows, reference dentition from suspect. The order is the answer.
• Why is the swab taken before the cast? Because the cast material (silicone) contaminates the bite surface and destroys the salivary DNA recovery window. Swab first, always.
• What is the current scientific status of bite-mark uniqueness? Class evidence, not individual. NAS 2009, PCAST 2016, ABFO walked back the claim. Indian SFSL practice reports "consistent with" or "inconsistent with" and lets DNA carry the identification.
• Which Indian case is the standard citation on bite-mark admissibility? Mohammad Aman v State of Rajasthan (2017). The point of the citation: admissible as corroboration, not as primary identification.
• What is the Iannarelli system and what is its current status? Twelve pair-wise ear measurements proposed in 1989; FearID and other reproducibility studies found inter-examiner agreement around 90% on the most discriminating measurements; treated as class evidence in mainstream forensic science; retained in Indian teaching as a class-evidence example.