Rugoscopy: Human identification by computer-assisted photographic superimposition technique

Human identification has been studied since fourteenth century and it has gradually advanced for forensic purposes. Traditional methods such as dental, fingerprint, and DNA comparisons are probably the most common techniques used in this context, allowing fast and secure identification processes. But, in circumstances where identification of an individual by fingerprint or dental record comparison is difficult, palatal rugae may be considered as an alternative source of material.

The present study was done to evaluate the individualistic nature and use of palatal rugae patterns for personal identification and also to test the efficiency of computerized software for forensic identification by photographic superimposition of palatal photographs obtained from casts.

Two sets of Alginate impressions were made from the upper arches of 100 individuals (50 males and 50 females) with one month interval in between and the casts were poured. All the teeth except the incisors were removed to ensure that only the palate could be used in identification process. In one set of the casts, the palatal rugae were highlighted with a graphite pencil. All the 200 casts were randomly numbered, and then, they were photographed with a 10.1 Mega Pixel Kodak digital camera using standardized method. Using computerized software, the digital photographs of the models without highlighting the palatal rugae were overlapped over the images (transparent) of the palatal rugae with highlighted palatal rugae, in order to identify the pairs by superimposition technique. Incisors were remained and used as landmarks to determine the magnification required to bring the two set of photographs to the same size, in order to make perfect superimposition of images.

The result of the overlapping of the digital photographs of highlighted palatal rugae over normal set of models without highlighted palatal rugae resulted in 100% positive identification.

This study showed that utilization of palatal photographs is highly viable. The photographic superimposition technique using Adobe Photoshop 8.0 software (used in this study for comparison of palatal rugae) was proved effective for human identification and can be used when ante-mortem data regarding palatal rugae is provided. This study also concluded that palatal rugae are highly individualistic and play an important role as a complementary method in personal identification.