Forensic identification presumes a multidisciplinary approach. It brings together experts from different fields including forensic pathologists, forensic anthropologists, forensic odontologists, serologists, criminalists, lawyers or other professionals, if necessary. This becomes obvious especially in disasters including a large number of victims such as wars, natural disasters etc. (1-3). On such occasions, apart from the application of the usual methods of identification, some alternative methods have been proposed for establishing the identity of victims (4, 5).
Cheiloscopy (from the Greek words cheilos - lips and skopein - see) is a forensic research technique that deals with the study of lip prints, their elevations and depressions that form a distinctive pattern on the outer surface of the lips (6, 7). Lip prints consist of patterns of cracks (sulci labiorum) in the form of elevations and depressions on the labial mucosa present in the transition zone between the inner labial mucosa and outer skin (8). They can be identified in the sixth week of intrauterine life and their pattern is rarely changed (9). Minor trauma such as inflammation or herpes, will not have a pronounced effect on the appearance of the lips and adjacent tissues, while greater trauma such as surgical treatments and scarring may affect the size and shape of the morphology of the lips (10). Lip prints are unique (11, 12). Lip prints of parents and children as well as those of brothers and sisters show some similarities (13). The importance of cheiloscopy is related to the fact that the lip prints are different in individuals (6). Identification of individuals is one of the most challenging parts of modern forensic medicine. Consequently, the analysis of lip prints has gained importance in forensic dentistry (14).
Determining the identity of a person can be a very difficult process. Dental, fingerprint and DNA comparisons are probably the most common techniques used in this context, allowing fast and reliable identification process. However, since they may not always be beneficial, it is sometimes necessary to apply some less well-known techniques (15). The positive identification of living or deceased persons using the unique features and characteristics of the teeth and jaws is a corner stone of forensic dentistry. Researchers often receive information for possible use as evidence. They gather information from different branches of dentistry. In addition, anthropometry, fingerprinting and other techniques are used to determine the gender, age and height. Today, researchers can rely on lip imprints thus facilitating the identification of possible suspects (7).
In 1902, Fischer was the first researcher who described the use of lip prints for personal identification and crime investigation (16). The imprint of lips is analogous to the fingerprint (17). The prints found at a crime scene can establish a scientific basis for identification. The assumption is that they would reveal the nature of crime, the number of people involved in it, the gender, the use of cosmetics as well as habits, occupational characteristics and the pathological changes of the lips themselves (15). Forensic science refers to scientific fields and disciplines that can be used in the court and have been generally accepted as reliable both by trial judges and by the relevant scientific community to distinguish truth from falsehood (18). In the process of identification, oral cavity allows countless possibilities. Lip prints are important because they are unique and do not change during the life of a person (8). In practice, the imprint of the lips can be found on the surface of the window, painting, doors, plastic bags, cigarette butts, etc. Finding lip prints is not difficult. In fact, latent lip prints can be easily viewed using a fluorescent dye (6). There are various classifications of lip prints: Martin Santos classification, Renaud classification, Afchar Bayat classification, Jose Maria Dominguez's classification. However, the classification made by Suzuki and Tsuchihashi is the most commonly used classification for recording the pattern on the lips. (6). Lip prints are classified into five types (19).
The purpose of this research was to analyze the lip drawing of the Croatian men and women in order to create the preconditions for forensic identification based on the analysis of the lips. The aim of the research was:
to determine the type of grooves on healthy lips of men and women by analyzing lip prints in a sample of Croatian population.
to determine if there is a statistically significant difference between men and women in the types of grooves.
to determine if there are any differences between male and female lip prints.
Materials and methods
The study included 50 women and 40 men from Croatia. Respondents were informed about the purpose and objectives of the research and were subsequently asked to participate in it. After the signed informed consents were collected, lips were photographed with centimeter caliper using a digital camera “Olympus μ – mini”. The respondents were asked to put a matte red lipstick on, (“Catrice 080 My Red Card”) using a mirror. The lipstick was treated with alcohol wipes (“Alkotip”) and left for 1 minute to dry. This was followed by taking lip prints on 100-gram white paper with a subject slightly opening his/her lips and lightly pressing centrally first, and then laterally on the paper. To remove lipstick, the respondents were offered dry cotton rolls and water. All collected samples were covered with a transparent adhesive tape and digitally photographed. The samples were stored in the Department of Dental Anthropology of the School of Dental Medicine University of Zagreb, Croatia.
Lip print patterns were analyzed according to Tsuchihashi Classification by using a magnifying glass (increase in magnification of 3ﾗ) (19). The grooves on lips were classified as follows:
The chi-square test and the Fisher's exact method were used for testing the statistical difference between male and female subjects and the types of groves. The level of significance was set at p<0.05.
A total of 90 people (50 females and 40 males) participated in the study. The study included only individuals with healthy lips and those without any visible signs of previous trauma. The research showed that most women had lip prints Type 2 (40.0%), followed by Type 1 (34.0%). Type 3 (12.0%), Type 4 (8.0%) and Type 5 (6.0%) were much less frequent. Type 3 (35.0%) was the most common lip print pattern among males, followed by Type 2 (25.0%). A small number of men belonged to Type 4 (15.0%), Type 5 (12.5%) and Type 1 (12.5%), Table 1.
The chi square test with 95% confidence level (p <0.05 and 4 degrees of freedom) showed a statistically significant difference between males and females regarding the types of grooves. It can be concluded that the variables of gender and groove types are dependent. The Fisher's exact method (two-sided test) with 95% confidence level (p <0.05, α = 0.05, z = 1.96) also showed a statistically significant difference between males and females with regard to the types of grooves.
Although cheiloscopy is not useful for human identification in situations in which only skeletal remains are available, it can provide a valuable piece of legal evidence. As the number of unsolved criminal cases continues to increase, academics focusing on criminal law together with the experts working as practitioners in criminal law seriously consider any new method for gathering information and providing evidence which will be crucial to effective solving of crime. Lip print varies in different parts of the lip, which points to the fact that every individual has a unique print of his/her, lips. It is assumed that a pre-mortem lip print can be compared with the post-mortem lip print for personal identification (20). Personal identification is established by comparing ante-mortem data with data obtained from autopsy. Few studies are available on the use of lip prints as evidence in personal identification and criminal investigation in forensic dentistry. Despite a small number of available studies, the study of Tsuchihashi is the standard for classification of different types of lip prints (21). Suzuki and Tsuchihashi classified lip prints into five types according to the shape and course of grooves. This classification is the most widely used classification system for analyzing lip prints (19).
The earliest accounts of the use of forensic dentistry in legal cases in the developed countries of Europe and the United States date to the 1950s and 1960s (22). Cheiloscopy is a relatively new field among the large number of identification tools available to the forensic expert. Although cheiloscopy can provide useful evidence in forensic cases, limitations still exist in the use of lip prints. A method of standardization need to be developed for assessment of lip prints (7). Lip prints can be detected as stratified surface traces with visible elements of lines (grooves). In such a case, the traces have the form of a print. Their features allow identification of specific individuals. If the lines are not clear (only a lip shape is printed) individual identification based on the lip print is very difficult, unless the trace contains other individual characteristics such as scars. In such cases, it is possible to examine the substance that makes a trace such as saliva in which it is possible to search for DNA. If the lips are covered with the remains of food or cosmetics and the lines are printed, an unclear trace will take the form of stains and can be subjected to chemical testing to determine which substance is covering the lip print. The value of the trace will depend on its type. Traces with clean lines and individual components are used to enable subsequent analysis and identification of human beings. It is not difficult to find the clue. Techniques used in fingerprints analysis can be employed for this purpose. By far the best way to detect traces is to use a powder and gently apply it to the foil. In order to fully utilize the potential role of cheiloscopy in forensic investigations, more research is needed on different population groups. In addition to this, variations need to be analyzed and a database should be set up. There is a great need to standardize protocols (8).
Randhawa, Narang and Arora reported that women belonging to Type 1 (59.48%) are predominant in population living in north India, followed by those belonging to Type 2 (12.54%) and Type 3 (11.89%). In men, Type 3 (41.52%) is predominant, followed by Type 1 (37.71%) and Type 4 (9.68%). The chi square test was applied when testing lip drawings. The results showed that there were significant differences between men and women with regard to the types of grooves (7).
The results of this study showed that most women in Croatia belong to Type 2 (40%), followed by Type 1 (34%). Most men belong to Type 3 (35%) and Type 2 (25%). The statistical analysis of the data showed that there is a statistically significant difference between men and women with regard to the types of grooves.
The results of this study provide insight into patterns of lip prints in the Croatian population. The fact that lip prints can positively distinguish individuals and hence have potential use in human identification was confirmed. The results of our study show that there is a statistically significant difference in incidence of certain types of lip grooves between men and women. In addition, the fact that lip prints are unique to each individual was confirmed.