An alternate novel approach to classify lip prints

Abstract

Abstract Background The wrinkles and grooves present on the sulci labiorum of human lips form characteristic patterns. As previous authors claimed, these can be used for personal identification in forensic cases because they are unique, permanent, and classifiable. Many scientists had devised different systems to classify the lip prints (Suzuki and Tsuchihashi, Martin Santos, Renaud, Afchar Bayar, and Jose Maria Dominguez). These systems were based solely on the shape of patterns present on the whole lip. However, sometimes, lip prints affected by either habitual smoking or any other pathological conditions are encountered. The investigator may have to form an opinion on partial lip print to identify the culprit. Therefore, in the present study, an alternative comprehensive system to classify even the partial prints has been proposed. Lip print samples were collected from 500 individuals (400 females and 100 males, respectively) using the tape lifting method. The whole lip print (Klein’s zone) was divided into 10 quadrants (five each on upper and lower lips) to study the whole pattern area thoroughly. The sample-wise and quadrant-wise frequency of all the patterns was statistically calculated. Sexual dimorphism of the lip print patterns was also assessed statistically. Results The method used emphasizes the consistency of patterns, which have been divided into Basic and Combination Patterns. Detailed examination of lip prints revealed that all the quadrants tend to have 7 types of Basic Patterns and 43 types of Combination Patterns despite similar appearance. These patterns can be further categorized into various subtypes based on the direction and orientation of wrinkle lines constituting the original pattern. Most of the Basic and Combination Patterns were widely distributed in all the analysed lip print samples and showed significant dependence on the sex of the subject. Conclusions The lip print patterns examined in the present study can be useful as an alternative to the existing systems to classify even partial lip marks recovered at the crime scene.