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Could we reconstruct a murder scene from the residual information in their retina, or (more likely) their visual processing centers?

The last thing Alfred (the butler) ever saw was the face of their killer. If this were a society like the United States or China, with pervasive, intrusive surveillance, be it corporate or state-sponsored, it would be a simple question of asking the crime scene for the killer's unique identifier.

Unfortunately, this is Switzerland. Thanks to their frankly paranoid data privacy laws, we literally have no access to the environmental datastreams leading to the crime. However, our high-tech society has another potential path: the victim's eyes and brain. Sure, they're dead. But (assuming the head of the victim is intact) can we get the last few patterns etched into their retinas or their brain?

Paper on Visual reconstruction of stimuli presented to a rat brain.

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  • $\begingroup$ Does this mean the surveillance data exists but isn't available through legal means, or that there is no such data in Switzerland? $\endgroup$ Commented Apr 22, 2016 at 16:49
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    $\begingroup$ If this had the "Science-Based" tag, the answer would be absolutely not. However, it has the "Reality-Check" tag, but there's no information about your reality. Is such a procedure already possible in your reality? Is this just a question about data privacy? $\endgroup$
    – Schwern
    Commented Apr 22, 2016 at 16:52
  • $\begingroup$ @Schwern, I'm perfectly ok with well-argued negative answers, I lean towards a negative answer myself, but one never knows... I recall reading about rats being killed and visual patterns being extracted from their dead brains... $\endgroup$ Commented Apr 22, 2016 at 16:54
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    $\begingroup$ I'm not sure the [crime] tag even applies, because presumably the answer would be the same regardless of the nature of the act observed, but I certainly think the [death] tag applies. $\endgroup$
    – user
    Commented Apr 22, 2016 at 17:42

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Probably not. In the rat experiment, the stimulus was a very extreme one, designed to maximize response. Visualizing a human face is a lot more subtle. The actual luminosity and color differences between human faces is markedly small, especially within a race. Another issue to consider is that the human eye rarely focuses on one point. It's constantly darting around with the expressed intent of undoing the rhodopsin based masking that our eyes do to manage contrast. If you were really careful, you might be able prove that, yes indeed, the killer had a face, but that might be it.

The really interesting parts of facial recognition occur much further into the visual processing process, where features of the face get identified and matched to other's faces. This would be where you would want to do such a facial recognition from their dead brain. However, there's a catch: its different for every person. Sure, there's regions that we know deal with faces, but the exact handling of each face is unique to an individual as early as when they begin recognizing their mother's face as an infant.

If I wanted to make a believable story involving such facial recognition, I'd suggest you have to prepare for it ahead of time. High value individuals might choose to undergo a twofold training process:

  • One part is undergoing mapping of their brain while being presented with real and simulated faces. This would help develop a "fingerprint" of how their brain does facial recognition, which could be kept on file. When they die, this fingerprint would help police map the neural pathways to better identify what face the victim recognized.
  • The other part would involve learning how to write your dying words into your brain itself! We've seen plenty of stories where the victim writes the killer's name in their blood as they are left on the floor. What if you could train yourself to scar the killer's name right into your brain with massive releases of chemicals making permanent changes in places where the police know to look? Sure, it's only an eyewitness testimony, not technically the eye witnessing the killer's face, but it might be a big part of solving the crime!
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    $\begingroup$ But if the killer didn't have a face, you would have a very easy time catching who the culprit was. $\endgroup$ Commented Apr 22, 2016 at 17:45
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The last time I can think of this coming up in fiction was in the atrocious Wild Wild West movie. They solve a murder by shining a light through a dead man's head to reveal the last thing he saw. Don't watch the movie, just watch this clip. This is the commonly understood idea of how it might work, and it's wrong, but it is most definitely a man's head.

What you're asking about is optography, the idea that the eye records the last image before death. While there was a lot of quackery that you could get it by simply photographing a dead person's eyes, you can't, there is some scientific basis to this.

Under ideal circumstances it has produced information... from rabbits. Wilhelm Kühne in 1878 claimed some success, though it's hard to separate his results from wishful thinking. When there was any success it required special preparation. The rabbit's eyes had to be covered to allow a build up of rhodopsin, they were made to stare at a high contrast target for minutes, and their eyeballs were quickly sliced and put into a solution. The process is analogous to fixing a photographic negative.

Here's Kühne's own notes on one experiment.

An albino rabbit, after being kept 15 min. in the dark, was decapitated; one eye was removed from the head under sodium light...and fastened onto the edge of a cork by means of needles...[The eye was placed in a] dark chamber with the cornea pressing softly against the diaphragm. The image was visible on the sclerotic, on one side of the optic nerve...that I was sure that it fell on the more deeply coloured division of the retina and could readily mark its place in the appropriate quadrant. Thereupon the yellow curtain was removed from the pane and the eye after five minutes' exposure was taken away, divided along the equator and examined in feeble gaslight....I brought the preparation out into darkened daylight and shewed it to several witnesses. There was evident on the retina a most distinct brighter diffused spot, the small dimension of which corresponded to those of the image previously seen by me, and the position of which made me already sure that it was the optogram.

The lack of a double-blind in his experiments (ie. Kühne knew what the rabbit was looking at when it died) means Kühne's own sketches of what he claimed to have seen in the rabbit's eyes could have been influenced by what he already knew the rabbit had seen.

This was never successfully performed on humans, though not for lack of trying. Optography as a forensic technique was re-evalutaed in the 1970s. While they were able to reproduce some of the results on specially prepared rabbits with high-contrast images, their conclusion about its use for forensics was...

If any, the scientific importance and benefit of optography is rated as minimal today. Historical considerations of using optography as a forensic instrument have never been realized.

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  • $\begingroup$ Sure, but how about extracting the information from glucose use patterns in the visual centers? $\endgroup$ Commented Apr 22, 2016 at 17:29
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    $\begingroup$ @SerbanTanasa Any form of "extract the image from the victim's brain" would require a far, far, far, far greater understanding of the brain then we possess and it would require that you get at the brain very, very quickly and destructively. Our knowledge of the brain is very poor. Even then there's no reason the brain will stop trying to process visual information at the "moment" of death. Like the rest of your organs, it will keep going until it's starved of oxygen and glucose. $\endgroup$
    – Schwern
    Commented Apr 22, 2016 at 17:33

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