Forensic Dentistry: Bite Mark Analyses On Live Human Subjects

Objectives: Bite mark analysis has historically been an integral component of criminal investigations. Currently, it is used as exculpatory evidence, which may be helpful in narrowing the search of suspects. However, its validity is affected by the factor of time. Moreover, previous studies evaluating bite marks have focused on cadavers or pig skin, which affects their credibility.
Methods: To address these limitations, we have recruited live human subjects and evaluated the window of time (critical period) after a bite mark is generated in which it could yield admissible evidence. A total of twenty-four subjects (11 males and 13 females) ranging in age from 21 to 71 years old participated in the study. A mechanical bite was applied by a denture mounted to a pressure indicated vice grip. Impressions were taken immediately following the bite and at 6, 12, 20, 30 and 45 minutes later. Measurements were recorded using a Proscan 2100 laser scanner.
Results: Changes in volume and height of the mandibular central incisors were calculated. Statistical analysis of the data was done using a least means squared analysis and the Wald χ² for the Type 3 GEE regression model. The data was analyzed for the sample population as well as for the subcategories of gender and age. Changes in volume (mm³) and height (µm) were inversely correlated with time (p<0.0001). Nevertheless, no statistically significant differences were observed for changes in volume (p = 0.26) or height (p = 0.109) between gender and only a marginally significant difference in volume was observed between age (p<0.041). In contrast, changes in the height of the mandibular central incisors were significantly affected by age (p<0.0001).
Conclusions: Supporting the importance of time awareness as an essential component of any criminal investigation, the critical period for achieving an adequate impression was determined to be less than 45 minutes (p<0.0001).