Hal’s answers 3

WARNING: this post contains graphic photography!
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Bluedog89 asked about lifting fingerprints from an eye and also can an eye capture an image at the time of death. Wow… interesting questions! Frankly, I am no fingerprint expert.  Richard Case or Joe Giacalone could speak with far greater authority on this topic, then myself.

I am not actually aware of anyone successfully lifting a fingerprint from an eye, but that’s not to say it has never been done.  I will have to inquire of my colleagues!  A few factors to consider;  anything wet is typically not a very good medium for a print, however fingerprints have been successfully located on submerged items.  I would imagine that an eye in the early stages of drying due to fluid evaporation would provide a better surface for a latent print that a fluid covered eye.  But, there is probably little call for development of a latent print deposited post-mortem (versus deposited anti-mortem) upon a dried, decedent’s eye.

The scenario is further complicated by the nature of our curvi-linear bodily surfaces and the softness of our skin.  Body surfaces are problematic for many reasons;  we are “shredding creatures” and constantly casting off bits of the body (hair, skin cells, etc). which does not suggest a good location for obtaining  for fingerprints.

The softness of the eye (and skin) also distorts.  For example, draw a small straight line on the back of your hand with a pen;  twist the skin just a tiny bit and notice the rapid distortion.  Next, lightly grab your right forearm with the fingers of your left hand and notice the rapid distortion of the surface.  Add to that environmental conditions such as rain, sweating and in our death cases, temperature change and decomposition wherein skin can slough, or stretches under gravitational pressure in decomposition fluid filled cavities called bullae (see attached image).  While experts have successfully developed prints from skin many, many times, it is more often than not, an ominous prospect.

Regarding “can the human eye to capture an image at the time of death”, the fact remains that exactly how our brain and memory actually works is still very mysterious and unanswered.  The “murderers photo developed and waiting to be uploaded from  the homicide victim’s eye” or so-called optogram, has been a topic of fiction writers and scientists alike for many, many years.  Despite media depictions, to the contrary there is no-known reliable science behind the hypothesis.   ~Hal

Comments

  1. I have not personally observed or have any knowledge of lifting a print from the eye however, the eye can help investigators during the course of a criminal investigation.

    It is one of several factors that pathologists and investigators use to estimate the time of death. The eye fluid – Vitreous Humor – is the clear liquid found in between the lens and the retina. After you die, levels of potassium increase which causes the cornea to become cloudy. Vitreous Humor is extracted at autopsy and the pathologist will determine the level of potassium in the cornea and therefore estimate the time of death.

    Remember, estimating time of death is not an exact science. Several factors out of the control of investigators and pathologists can severely impact the estimate, such as clothing worn, weather conditions, and where the body is found. Unless the person dies hooked up to a monitor with a doctor in the room, the time of death will always be an “estimate.”

    Joe

  2. The question of fingerprints on an eyeball bothers me for 2 reasons.

    1. I get squeamish seeing someone insert a contact lense, so the thought of examining eyes for fingerprints doesn’t really appeal to me.

    2. I don’t have a definitive answer, but that won’t stop me having a damn good guess until I come across any published material……

    I agree with Hal that it would be extremely difficult to record a fingerprint off a working eye from a living person.

    The reasons being are that:

    a) The involuntary moistening of the eyes (i.e. tears) will likely destroy any latent prints left by sweat or any other fluid.
    b) You would not administer any development powders or chemicals to the eye.
    c) Fingerprints are often visualised using laser, which would damage an eye.

    The only chance would be an imprint into the eyeball made by sufficient force… if even possible?? Even then I don’t know if the eyeball is able to heal itself or how long that is likely to take, as it would require advanced photography by an optician to record the print.

    Now if the subject is deceased and the eyeball has been removed, then a few more options are open…..

    I recall reading somewhere that the texture of a human eyeball is similar to that of a tomato (pronounce it however you wish)…. and there has been some research (and case studies) of fingerprints being found on fruit… especially tomatoes. It seems the best form of development on these would be black or magnetic powders.

    Hal was quite correct to mention that some form of distortion is likely to take place; though this shouldn’t prove too difficult for an expert to consider during their examination as they should be made aware from the case notes that the print was recovered from an eyeball and make any necessary allowances.

    We had an optician deliver a presentation at a Fingerprint Society conference a couple of years ago…. but I never thought of asking those types of question. If I can find his contact details, I will ask his opinion.

    Richard

  3. Thank you Hal for answering my questions. I must admit that I was going on the basis of the “CSI effect” – seeing these tactics covered on TV shows made me wonder if it was possible.

    I thought the eye was too porous a surface to lift a print, but didn’t consider that an eye would dry out post-mortem. Thanks for clarifying.

    The optogram effect is probably too far-fetched, but makes for good drama. Too bad tho, it would be an excellent crime-fighting tool along w/CCTV & Google Earth cams.

    And Joe, thanks for mentioning Vitreous Humor in regards to estimating time of death. Another of the many tools pathologists & investigators have at the ready during the course of an investigation.

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