It is well-known that dental evidence plays a very important role in the identification of unknown bodies. Of this evidence, X-ray films are considered the most reliable and valid dental evidence. On the other hand, in recent years, digital X-ray photography techniques have been developed and applied in the field of clinical dentistry. We investigated the application of the direct digital X-ray system to dental personal identification through the use of Compuray (Yoshida Dental Trade Dist., co., Ltd.). The research results can be summarized as follows:
1. We can easily obtain and maintain clear digital X-ray images if compressed images are transmitted through computer networks.
2. We can obtain same-angle X-ray images as post-mortem dental evidence to ante-mortem X-ray photographs on the monitor in a short period of time through the use of Compuray.
3. The comparison between ante-mortem and post-mortem X-ray images can be made easily through magnification and superimposition.
4. As a result of the development of transportable equipment, it is possible to conduct a detailed comparison and examination in real time, next to an unknown body.
In this time, we present two murder cases using Compuray for personal identification of victims.
CASE 1: On September 14, 1997, a dead body of a female was found on a path in Chiba Prefecture. As a result of judicial autopsy, the cause of death was asphyxia by strangulation. Although the body and clothes were intact, because the postmortem interval was estimated only several hours, due to the insufficient information for any positive identification, Chiba Prefectural Police Headquaters requested a examination by dental findings to us. The examination was carried out at soon, and the X-ray examination was performed using the Compuray beside the body. As a result, we judged the body's age was 17(}1) years old from calcification degree of unerupted mandibular third molars and others.
CASE 2: On March 2, 1998, a human skull has been found from a trolley-net of a fishing boat, on the coastal waters of Japan, in a 27.3 nautical miles from Inubosaki Lighthouse. The skull has then been send to us from Japanese Coastguard Choshi Division, to be checked against the data of a specific person, who has been claimed "missing" since a month ago. Compared between the skull and the dental ante-mortem X-ray films and records supplied by the dentist of the person, we have found many identical points between the two, especially in regard to the X-ray findings, which supported the idea that the skull belongs to the missing person.
In the CASE 1, we have taken a total number of about 20 digital images of different parts of the remains from various angles. The direct digital X-ray system has enabled us to get all these pictures complete in just five to six minutes. We have also taken, in the CASE 2, a number of pictures from various angles, all of which has been completed within a remarkably short period of time.
Key words : Personal identification, Direct digital X-ray system, Forensic odontology