Tears and Eyewear in Forensic Investigation-A Review

Body fluid analysis has played a crucial role in ascertaining various characteristics and has greatly aided in reconstructing events during crime scene investigation. It is often presumed that crimes that involve violence and mental disturbances such as murder or sexual assault provide good sources of body fluids such as blood, saliva, semen, vaginal secretions, urine and tears. Tears are secreted in response to any emotional or stressful situations and may be found deposited on surfaces such as bedding, tissue paper or cloth. In the absence of the commonly noted body fluids such as blood or saliva, tears can play an important role that can lead to personal identification by examining the biochemistry and molecular aspects to obtain a full DNA profile. Additionally, identification of an individual may be done by carefully observing certain unique eye characteristics such as heterochromia which is highly individualistic. Characteristics of eyewear such as spectacles and contact lenses have unique properties and prescription criteria for correcting an individual's eyesight that can provide vital clues in understanding the visual ability of an individual. In crime scene investigation, the presence or absence of eyewear provides immense evidentiary value that has greatly aided in solving cases such as Janet Abaroa's Murder. This paper provides a systematic review of the possibility of using tears and eyewear for the purpose of forensic investigation and to statistically support the inferences with prescription databases which may be initiated across different populations. Forensic Optometry is yet to get streamlined along with the routinely followed investigative techniques and scientifically explored although no standard protocols exist to analyse eyewear. The use of behavioural optometry is gaining attention in the context of driving laws of different countries and is a simple but powerful indicator of abnormal behaviour. It is speculated that the last seen image referred to as an 'Optogram' of an individual may be captured in the retina since our eyes functions like a camera. Although this claim is considerably unexplored, it is quite possible that the last seen image of a criminal, objects or a place may be noted that can positively help in linking individuals at the scene of crime or identify the primary crime location. In this review, the potential for new insights into the analysis of tears, eye and eyewear characteristics have been explored.