Characteristic Features of Ear and Ear-Prints in Forensic Identification

The human external ear is a morphologically perplexing structure with wide variations in its features across individuals. Advances in forensic science have established the use of morphological features and prints of different parts of the human body in establishing the identity of an individual. The present study aims to establish such an identification process by examining the use of comparative analysis of ear prints and ear photographs.

The study examined the morphological features of ear prints of 140 participants (71 males and 69 females) ranging in age from 18 to 25 years (with a mean age of 20.22 ± 1.77 years), recruited from a North Indian population. Prints of both the ears were recorded, using the inking method. The morphological features of the ear prints were compared with the photographs of the ear for their uniqueness and individualization using likelihood ratios.

The degree ofantihelix curvature demonstrated the highest correlation (98.57%) between the morphological features visible on the ear and the expressions of these features in an ear print. The impression of earlobes, Darwin tubercle, crus of the helix, and shape of the external ear showed accuracy between 70% and 90%, whereas correlations below 70% accuracy were recorded for the other features. The likelihood ratios for 12 parameters were reported to be more than 10x, representing that the identification made using these parameters was > 10 times more likely to be true identification as compared to false positives. Moreover, 5 parameters were found to show high sensitivity, with values greater than 3 standard deviations (0.997), with an additional 9 parameters found to have good sensitivity at values greater than 2 standard deviations (<0.95). Similarly, 2 parameters were found to show high specificity, with values greater than 3 standard deviations (0.997), with an additional 18 parameters found to have good sensitivity at values greater than 2 standard deviations (<0.95).

Elevated features of the ear, such as helix, antihelix, antitragus, tragus, and inter-tragic notch; particularly the degree of antihelix curvature, are more easily impressed and identifiable on an ear print. The results support that ear prints may provide important clues to assist in establishing the identity of an individual if several morphological features are evaluated concurrently.