Preliminary analysis of facial hair follicle distribution for forensic identification using OCT

In most deaths caused by explosions, the fragment of explosive remained on the victim's body can provide valuable clues to forensic investigation. However, the examination of the skin and appendages at the scene of explosion, which may reveal clue to the identity of an individual, has not been extensively studied. Compared with visual appearance of the epidermis surface that affected by various wounds, skin adnexa embedded in the dermis has a more stable morphology as an inner biometric. Hair follicles are formed when a fetus is 5 months old and distributed fairly evenly throughout the body, with the exception of hairless palms and soles. Therefore, we focus on the distribution of hair follicles in order to infer information of age, gender, and race/ethnicity. Optical coherence tomography (OCT) is a novel forensic imaging method, which achieves non-destructive, high-resolution and most importantly cross-sectional imaging. In this study, we design and develop a custom-built spectral-domain three-dimensional (3D) OCT system with a portable handheld probe to detect and reconstruct the hair follicles in the facial skin. We test our system on the forehead and preauricular skin of 2 adult volunteers and demonstrate the high quality visualization of hair follicles beneath the epidermis. The diameter, orientation, density and shape of hair follicles can be extracted from the 3D volume data. The preliminary analysis suggests that these parameters vary from different part of body and have individual difference. Eventually, we believe 3D OCT is promising tool for the examination of hair follicles for forensic purpose.