Evidentiary value of smile photographs from the internet for human identification: A pilot study

Objectives

Smile photographs retrieved from the internet can provide ante-mortem dental evidence to augment human identification. However, currently, the process is not validated and there is no agreed methodology. This study aims to evaluate the potential evidentiary value of dental data from these photographs for identification purposes.

Materials and methods

This study compared retrospective smile photographs from the internet with current smile photographs of ten (10) subjects using three (3) methods. 1. Conventional visual comparison of facial and dental features performed qualitatively noting the distinctive features. 2. Comparison of incisal edge tracings. 3. Semi-quantitative superimposition involving the computation of total correspondence scores and Index of Correspondence (IC). For each method, a score of 0–3 was allocated to score level of match. Matching scores were compared and statistically analysed.

Results

Individualising features could be visualised from smile photographs. For comparison, dental features visible in the photographs were reliable and consistent. Based on incisal edge tracing and dental superimposition, nine of ten current photographs were accurately matched to ones taken at an earlier time. Correct matches yielded significantly greater outcomes than incorrect matches when using incisal edge tracing and dental superimposition (p < 0.01). Grading outcomes from both methods are moderately positively correlated. Furthermore, both incisal edge tracing and dental superimposition significantly improved correct match grades (p < 0.05).

Conclusion

Photographs of people smiling retrieved from the internet can show distinctive features of the dentition. Semi-quantitative parameters can enhance the amount of dental information obtained from photographs which may assist in identification. Several methods are proposed to maximise information extracted from photographs.