Freeform Fabrication Assists Forensic Scientists in the Identification of Unknown Victims

摘要

According to the International Homicide Investigators Association, there are currently over 40,000 unidentifiedrnbodies being held in coroner?s and medical examiner?s offices across the United States. Over half are estimated to bernvictims of homicide, and all are awaiting positive identification. One technique utilized by forensic anthropologistsrnto establish the identity of unknown skeletal or decomposed individuals is the use of facial reproduction. In facialrnreproduction, soft tissue approximating muscle and skin is added to the skull in an attempt to reflect how thernindividual looked during life. Soft tissue depths at specific locations (i.e., certain craniofacial landmarks) are knownrnand have been standardized according to an individual?s sex, age, ancestry, and body type. For the most part, facialrnreproduction is still accomplished manually by adding layers of soft clay to represent tissue on the actual skull of therndeceased individual. This method is quite time-consuming (often taking two or more weeks) and often not feasiblernbecause the skull may be damaged, or the use of clay overlying the actual skull may destroy evidence. To overcomernthese limitations, researchers have recently turned to Computed Tomography (CT scan) technology to generate CADrnfiles of unidentified skulls, which are then modeled and recreated with rapid prototyping machines. One limitationrnof this method is that it is dependent on the initial CT scanning instrument, which is not portable and requires thatrnthe unidentified remains be removed from their original storage sites (typically morgue coolers or crime scenes) tornthe location where CT scanning instruments are available (often hospital or clinical settings). Because many of thesernunidentified remains are either skeletonized or are in various stages of decomposition, the transport of these bodiesrnto locations with CT scanning machines is often not possible or permissible. In this paper, we first propose a newrnmethod to rapid prototype skulls via stereolithography (STL) files generated by hand-held portable laser scanners, asrnopposed to using CT scanning machines. These rapid prototypes can then be fabricated for facial reproduction,rnnegating the use of the actual skull, and not requiring the body be removed from its original location. Also, resultsrnof the facial reproduction for an active case are presented. Secondly, we outline preliminary results of a newrncomputerized facial reproduction and superimposition method, which accurately models tissue depth and is notrndependent on the manual application of clay.