Optical Evidence in Forensic Investigation

Jagadheswari. V, M.Optom.

Assistant Professor, School of Allied Health Sciences, Salem, India.

The application of optical science to the judicial system is known as forensic optometry. It is used in court proceedings for identification, to test eyewitness accuracy, and to investigate how people’s vision may affect their ability to effectively judge a scenario.⁽¹⁾

Prescription eyewear, like glasses and contact lenses, is used by unique people. As a result, their physical characteristics and refractive error levels may be examined and compared for personalisation. In addition to the recommended values, the way that glasses, contact lenses, and other ophthalmic devices look at their surroundings might help connect certain circumstances to specific people or possible suspects. They can also be compared with pictures taken through surveillance or pictures taken from devices that have been kept. ⁽²⁾ In contrast to fingerprints or DNA, eyewear lacks the inherent uniqueness needed for individualisation.  Unique frames or prescription information may assist in reducing the number of potential wearers, but they are not as specific as other forensic evidence. ⁽³⁾

Devices for the eyes (glasses, lenses, contact lenses, intraocular lenses, corneal and iris implants, ocular prosthetics, etc.) can remain for years after the corpse has decomposed. The artifacts or their pieces must be found through a thorough examination of the remains and the surrounding area. ⁽⁴⁾

The iris biometric technology is widely used for both identification and access control. The reliability of the algorithm deteriorates when iris recognition occurs in a cadaver due to postmortem modifications. ⁽⁵⁾ High-security systems are increasingly utilising iris scanners since each person’s eyes are so different.⁽⁶⁾ Environmental factors determine the iris’s viability period, which can range from 4 days post-mortem in warmer seasons to over 50 days in winter. It has been demonstrated that post-mortem iris recognition of bodies stored in mortuary conditions is feasible 5–7 days after death, and sometimes up to 21 days.⁽⁷⁾

Different nations utilise different criteria for diagnosing death, but in general, pupil appearance and response are considered as criteria. The criteria in Australia, New Zealand, and Japan are bilateral unreactive pupils with diameters more than 4 mm. According to US and Canadian guidelines, pupils are usually dilated or midsized following brain death, although they do not require pupil diameters to be greater than 4 mm.⁽⁷⁾

The cornea is hazy or foggy around two hours after death, and during the following day or two, it becomes increasingly opaque. This makes it difficult to see the rear of the eye and the lens. However, this clouding might offer a rough approximation for estimating the time of death. ⁽⁸⁾

The vitreous, which lies between the retina and the crystalline lens, is a special and practical alternative matrix in forensic toxicology because of its limited vascularisation and relative isolation from other body compartments due to the blood-retinal barrier (BRB), which prevents materials from diffusing, secreting, or filtration.⁽⁷⁾

There are many chances to use your knowledge in this broad subject matter, whether you choose to work as an optometrist treating patients’ eyes and ocular conditions or want to collaborate with forensic scientists looking at evidence found at crime scenes.

References:

1. https://openaccesspub.org/advanced-forensic-sciences/forensic-optometry
2. Aparna, R., Iyer, R. S., & Thomas, M. W. (2023). Analysis of prescription eyewear for personal identification in forensic optometry. Forensic Science International: Reports, 8, 100326.
3. Sah, R. (2024). Eyewear in Forensic Investigations: Unveiling Evidence. International Journal of Medical Toxicology & Legal Medicine, 27(1), 115-119.
4. Bertolli, R., Berg, G. E., & Pannone, R. (2012). VISION SCIENCE IDENTIFICATION OVERVIEW. Forensic Examiner, 22(1).
5. Singh, J., Kaur, E., Dhiman, S., Kaur, J., Tripathi, H., Sood, A., & Rohatgi, S. (2022). Eye Optics: A Unique Blink in Forensic Identification. International Journal of Health Sciences, (III), 4188-4200.
6. Adebisi, S. (2009). Contemporary tools in forensic investigations: The prospects and challenges. The Internet Journal of Forensic Science, 4(1), 1-8.
7. Ang, J. L., Collis, S., Dhillon, B., & Cackett, P. (2021). The eye in forensic medicine: a narrative review. The Asia-Pacific Journal of Ophthalmology, 10(5), 486-494.
8. Murphy, John. (2004). CS eye: how the eye is used in forensic medicine, and how you can help detect and prevent crimes. Review of Optometry, vol. 141, no. 11.