Please welcome my fifth collaborator and guest blogger, Hal G. Brown. Hal Brown is the Deputy Director of the Delaware Office of the Chief Medical Examiner and states Forensic Sciences Laboratory, Wilmington, DE. Brown is also the Delaware Case Manager for NamUs Unidentified/Missing Persons.
Hal will be educating us about post-mortem and autopsies. He will be indicating what the limits of science are and what still can be done in cold cases. His blog posts reflect his own opinions and may not reflect those held by the Delaware Office of the Chief Medical Examiner.
Beware that Hal’s posts may include graphic photography. It is never the aim to sensationalize but to educate and inform. If one of his posts includes photography, it will be indicated at the top.
Warning: this post contains autopsy photography that some may find upsetting.
Post-mortem ocular changes are not conclusive post-mortem interval evidence.
The issue here is one of “scientific certainty”; the fact is, despite what is depicted on television, we cannot assess postmortem intervals with any degree of scientific certainty based solely on ocular changes alone.
The eyes often exhibit some of the earliest postmortem changes, as a result of stoppage of capillary circulation and settling of red blood cells. If the eyes remain open, a thin film or cloud can be observed within minutes on the surface. Typically, in about two or perhaps three hours postmortem, some corneal cloudiness will often present. However, if the eyes are closed, the corneal cloudiness or film (as it is sometimes called) may be delayed by many hours; we have seen corneal cloudiness delayed 15 or 20 hours in some cases, especially if the eyes were closed. Contacts can also alter the rate of post-mortem ocular change.
Generally speaking, in early postmortem stages, the sclera or white of the eye and the cornea will typically be normal or relatively clear (assuming the sclera and cornea were also clear before death). Over time, post-mortem ocular changes include clouding of cornea and “tache noir” (brown corneal surface from exposure to the environment between eyelids).
Clouding is not irrespective of environmental influences; a more arid environment will cause the eye to dry out much quicker. For example, a body in the desert with eyes open in broad daylight will likely have very rapid ocular decomposition changes and corneal clouding. Another way of stating this is that examination of ocular fundus after death can contribute to the assessment of time of death, but no conclusive evidence can be obtained about any correlation of fundus findings at the time of death.
Keep in mind, that after death, some cells and enzymes often continue to essentially live individually or collectively for a short period of time; the cornea continues to receive oxygen for metabolism, thus remains viable for a longer period than most other tissues/cells. The good news is that fortunately, this is the very reason that “eye banks” can successfully harvest a cornea many hours after death and transplants can thus occur!
The bottom line is that post-mortem ocular changes are absolutely not conclusive post-mortem interval evidence; rather they are supportive evidence when considered with all of the other post-mortem changes, circumstances and environment.