“Lip prints held potential promise as a supplementary tool along with other modes to recognise the sex of an individual” – Karn et al
From the paper, “Morphological patterns of lip prints in relation to gender in a defined cohort.”
When it comes to the scene of a crime, a question normally asked is whether the criminal has left any fingerprints which can be used to identify them. However, in one Japanese case, a burglar did not leave any fingerprints, but was still identified successfully out of five possible suspects. The reason: they drank from a glass of water at the crime scene. But it wasn’t DNA or some other high tech forensic method that captured the burglar. It was the lip prints they had left behind on the glass that sealed a conviction.
Cheiloscopy is the study of lip prints. These lip prints are lines and fissures (lines of breakage, such as cracks) present in the area of the lip between the inner labial mucosa (inside of the lip) and the outer layer of skin. The lip prints that someone has will remain with them for life and will be unchanged, just like fingerprints. They will be the same even if they undergo trauma or disease, such as herpes. Also like fingerprints, lip prints are unique and specific for one individual. Even the lip prints between identical twins will be different and the twin that the print belongs to can easily be identified (1). Naturally, it has been suggested that lip prints could be used in personal identification in a criminal court and forensic setting.
To assist in identification, lip prints are placed into 6 different categories depending on grooves, fissures and patterns. These 6 categories are:
- Type I – A clear-cut groove running vertically across the lip.
- Type I’ – A partial-length groove of Type I
- Type II – A branched groove
- Type III – An intersected groove
- Type IV – A reticular pattern
- Type V – Other patterns
Figure 1 – Categories of lip prints (2)
Researchers in Nepal have worked on analysing lip prints and evaluating whether they are from a male or a female. In this study, they looked at 70 males and 74 females. As expected, it was found that no one had a similar lip print pattern. The most frequent lip print pattern was type I and the least common was type V.
Amongst males, the most common lip print was type I and the least common was type IV. Amongst females, the most common was type II and the least common was type V. Using statistical testing method, it was determined that lip print patterns type I, II and V were significantly associated with gender. This means that if you were to test these print types, it would be possible to know whether it came from a male or a female. This would not be possible for types I’, III and IV. The table below shows some of the results from the experiment. It is important to remember that these results are just for one population of people and not the entire globe.
However, the experiment could be put into question as only the central area of the lower lip was examined. However, by a general consensus developed over decades of research, just like a fingerprint, examining a small area can determine a correct conclusion on who the print belongs to.
The use of lipstick does not even need to be considered when looking for lip prints because the edges of the lips have sweat glands that secrete fluids that allow for a concealed and invisible lip print to be present. These can be revealed using aluminium or magnetic powder.
Therefore, this investigation has shown that, within the cohort of people examined, it is possible to determine whether a lip print belongs to a male or a female depending on the print type. This explains how in 1987, the FBI captured a male bank robber who used lipstick to disguise himself as a woman when lip prints were analysed which were left on a glass door during the robbery (3). Further experiments need to be done to ensure that the same method can be used in identification for everyone globally and not just this small cohort of people.
— By Daniel Baird
(1) Sonal Vahanwala, and Sandeep Pagare. “Evaluation of Lip-Prints in Identical Twins” 12, no. 2 (2012): 192–96.
(2) Dineshshankar, Janardhanam, Nalliappan Ganapathi, MuniapillaiSiva Kumar, Ravi Aravindhan, ThukanaykanpalayamRagunathan Yoithapprabhunath, and Thangadurai Maheswaran. “Lip Prints: Role in Forensic Odontology.” Journal of Pharmacy and Bioallied Sciences 5, no. 5 (2013): 95. https://doi.org/10.4103/0975-7406.113305.
(3) Williams, T. R. “Lip Prints – Another Means of Identification” 41, no. 3 (June 1991): 190–94.