Identification is the key point for forensic analysis. There are many characteristics of human beings that are considered unique and important from the view point of forensics for the purpose of identification. Lip prints are one of those which are unique to an individual, similar to fingerprints, footprints and palm prints.
Identification of an individual is important in any case whether it is done by fingerprint, DNA, identity cards, dental patterns or Lip prints. Lip prints being a new addition in the field of personal identification is as effective as others due to its unique patterns.
What are Lip Prints?
Lips are soft, visible, fleshy folds of the mouth covered externally by skin and internally by mucous membrane. The mucous membrane shows numerous furrows and ridges which form a characteristic pattern called Lip Prints.
The study of lip prints is known as cheiloscopy or quieloscopy that deals with the study of the grooves or furrows present on the vermillion zone of human lips.
Study of Lip Prints
Lip prints were first mentioned by R. Fischer in the year 1902 who described the arrangement of furrows on the lips. Sir Edmond Locard was the first one to suggest the use of lip prints for identification purposes in 1932.
Further, Le Moyne Snyder (1950) and Dr. Martins Santos (1960) also supported the idea of lip print analysis for identification of individuals. A detailed study on lip prints was done by Suzuki in 1960, which was based on the shades of lipsticks and their removal techniques for the purpose of identification.
Later, Suzuki and Tsuchihashi in 1971, conducted a study and devised a classification system of 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 i.e., Upper lip and lower lip. They are further divided into 6 parts (3 parts each). Both the parts have various characteristic features of grooves on them such as – fence-like crossings, bifurcating lines, double fence-like crossing, cross lines, delta-like opening, star like lines, triangle/pentagonal/hexagonal shapes, etc.
UL -Upper Left; UM -Upper Middle; UR -Upper Right
LL -Lower Left; LM -Lower Middle; LR -Lower Right
Classification of Lip Prints
In 1967, Santos classified the furrow patterns of the lips in the following categories:
- Straight Line
- Curved Line
- Angled Line
- Sine-shaped Line
The current method to classify lip prints is based on Suzuki and Tsuchihashi classification that classifies lip prints into 6 categories:
- Type I
The print has a clear-cut groove running vertically across the lip.
- Type I’
The print shows a partial-length groove of Type I.
- Type II
Lip print shows branched grooves.
- Type III
Intersected grooves are observed in this pattern.
- Type IV
The prints show a reticulate pattern.
- Type V
All the other patterns which can not be classified in the above mentioned types are included in this category.
Like fingerprints, three types of lip prints are also found on the crime scene, i.e., visible prints (usually stained with lipsticks), latent prints and 3-D prints.
Visible prints and 3D prints are easy to locate but latent prints are difficult to trace. Therefore first the latent prints are made visible and then collected.
Visualizing Lip Prints
The methods used for visualizing lip prints include physical methods, chemical methods and X-Ray method.
Physical method involves the use of various powders such as aluminium powder, magnetic powder and plum-carbonate powder. The powders are dusted on the suspected area of prints which get stuck to the natural oils of the prints and makes them visible.
In chemical methods, chemicals like Lysochrome dyes and small particle reagents are used for developing latent lip prints. These chemicals react with the natural oils of the lips and show visible prints.
X-Ray method can be used for developing latent prints by spreading lead powder on the suspected area and then applying x-rays on that area. The x-ray film is then treated with chemicals which shows the lip prints on it.
Collection of Lip Prints
The lip prints from the crime scene are collected using photography and transparent tape-lift methods.
Lip prints from the suspects are collected through photography of their lips or by applying lipstick or lip rouge on their lips and directing them to press their lips on the cellophane sheets.
Comparison and matching of the groove patterns on the lips forms the basis of analysis of lip prints which helps in individualization.
The information elucidated by the lip prints is useful in determining the race, sex and unique identity of an individual.
Lip prints are acceptable in forensic dentistry as an identifying characteristic. The Federal bureau of investigation (FBI) and the Illinois state police consider that lip prints are unique like fingerprints and are positive means of identification.
With the advancements in technology now lip prints are included in biometrics. Softwares like Adobe Photoshop 7 software serves as a convenient method that provides better visualization and ease in recording and identification of the lip prints.
It also permanently stores the data of lip prints that can be helpful in keeping the ante-mortem records of an individual. Weighted Value Scoring system is used to calculate the score of the lip print patterns which is helpful in identification and individualization.