Personal identification using lip prints in an investigation

Identification is the key point of forensic analysis. Many characteristics of human beings are considered unique and important from a forensic perspective for identification purposes. Lip prints are one of those that are unique to an individual like fingerprints, footprints, and palm prints.

The identification of an individual is important in all cases, whether it is done by fingerprints, DNA, identity cards, dental patterns or lip prints. Since lip prints are a new addition in the field of personal identification, they are as effective as the rest due to their unique designs.

What are lip prints?

The lips are soft, visible, fleshy folds of the mouth covered on the outside by skin and on the inside by a mucous membrane. The mucous membrane has many furrows and ridges that form a characteristic pattern called Lip Prints.

The study of lip prints is known as cheiloscopy Where quieloscopy which deals with the study of furrows or furrows present on the vermilion area of ​​human lips.

Study of lip prints

Lip impressions were first mentioned by R. Fischer in 1902, who described the arrangement of furrows on the lips. Sir Edmond Locard was the first to suggest the use of lip prints for identification purposes in 1932.

Additionally, Le Moyne Snyder (1950) and Dr. Martins Santos (1960) also supported the idea of ​​lipprint analysis for the identification of individuals. A detailed study of lip prints was done by Suzuki in 1960, based on lipstick shades and their removal techniques for identification purposes.

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Later, Suzuki and Tsuchihashi in 1971, conducted a study and devised a classification system for lip prints. Kasprzak (1990), conducted a research for 5 years on 1500 people to elaborate the practical use of lip prints as individualizing characteristics.

The lips of human beings consist of two parts, namely the upper lip and the lower lip. They are divided into 6 parts (3 parts each). Both parts have various characteristics of grooves such as – fence-shaped crossings, bifurcating lines, double fence-shaped crossings, transverse lines, delta-shaped opening, star-shaped lines, triangular/pentagonal/hexagonal shapes, etc

UL – Top left; UM – Upper middle; UR – Top Right

LL – Bottom left; LM – Lower Middle; LR – Bottom right

Classification of lip prints

In 1967, Santos classified lip furrows into the following categories:

  • Straight line
  • Curved line
  • Inclined line
  • sinusoidal line

The current method of classifying lip prints is based on Suzuki and Tsuchihashi’s classification which classifies lip prints into 6 categories:

  1. Type I

The print has a sharp groove running vertically across the lip.

  1. Type I’

The print shows a Type I partial length groove.

  1. Type II

The lip impression shows branching grooves.

  1. Type III

Intersected grooves are observed in this pattern.

  1. Type IV

The prints show a reticulated pattern.

  1. V-type

All other models that cannot be categorized into the types mentioned above are included in this category.

Like fingerprints, three types of lip prints are also found at crime scenes, namely visible prints (usually smeared with lipstick), latent prints and 3D prints.

Visible prints and 3D prints are easy to locate but latent prints are difficult to trace. Therefore, latent fingerprints are first made visible and then collected.

Visualize lip prints

Methods used to visualize lip prints include physical methods, chemical methods, and X-ray method.

physical method involves the use of various powders such as aluminum powder, magnetic powder, and plum carbonate powder. Powders are dusted on the suspect area of ​​the prints which stick to the natural oils in the prints and make them visible.

In chemical methods, chemicals like Lysochrome dyes and small particle reagents are used to develop lip latent prints. These chemicals react with the natural oils in the lips and show visible imprints.

X-ray method can be used to develop latent prints by spreading lead powder over the suspect area and then applying x-rays to that area. The x-ray film is then treated with chemicals which show the lip prints on it.

Collection of lip prints

Lip prints from the crime scene are collected using photographic methods and transparent tape.

Suspects’ lip prints are collected by photographing their lips or by applying lipstick or lipstick to their lips and asking them to press their lips to the cellophane sheets.

Comparing and matching groove patterns on the lips is the basis of lip print analysis which helps in individualization.

The information elucidated by lip prints is useful in determining an individual’s race, gender, and unique identity.

Lip prints are acceptable in forensic dentistry as an identifying feature. The Federal Bureau of Investigation (FBI) and the Illinois State Police consider lip prints to be unique like fingerprints and to be positive means of identification.

With advances in technology, lip prints are now included in biometrics. Software like Adobe Photoshop 7 software is a convenient method that provides better visualization and makes it easier to record and identify lip prints.

It also permanently stores lipprint data which can be useful in maintaining an individual’s ante-mortem records. The weighted value scoring system is used to calculate the lip print pattern score, which is useful for identification and individualization.

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