Does the absence of gravity affect rigor mortis? Seeing how you can figure out the approximate time of death based on how much blood has pooled in the gravity facing side of the body, how does lower gravity or even the absence of gravity affect this?
I'm just thinking about murder mysteries in space and the possibilities they hold.
Also, mirrored on CotI.
It's been a while since I had my Forensic Pathology classes, and I have no formal instruction on zero gravity biology, but those are my best guesses.
Rigor mortis is still there, and probably on a similar time scale, unless zero-gravity cell death is any different.
No blood pooling without gravity, probably. Which would mean that you cannot use it to estimate time of death.
First off, what a cool question!
I don't know much about biology, but zero-gravity is typically a misnomer. When you are talking about space stations (ie: the ISS) the astronauts typically are at .9g and weightlessness is generated by an endless freefall to earth. This can have all sorts of crazy implications on biology.
(Youtube shows me this: http://www.youtube.com/watch?v=jTL_sJycQAA .. even more strange implications than I thought)
However, I would hazard a guess that The Butcher is right, given an atmosphere and constant human-normal temperature biochemistry would still happen. Prolonged exposure to hard vacuum would change stuff, the bacteria in would probably get fried or go dormant due to massive radiation dosage and extreme temperatures .. in deep space you would freeze long before decomposition and be a beautiful corpse for until you hit something.
Typically in a weightlessness situation liquid doesn't fall but just hangs out due to surface tension. I would also imagine blood might still pool in the direction of any centrifugal force (if it was greater than the local gravity), but I am not sure.
It is a very cool question indeed.
Couldn't you try to analyse how long the body's been in space based on radiation levels?
Another cool question.
All I knew was that a Sievert was the (SI) unit for radiation exposure on human tissue. And a quick google came up with this quote:
QuoteEffective Dose
The probability of a harmful effect from radiation exposure depends on what part or parts of the body are exposed. Some organs are more sensitive to radiation than others. A tissue weighting factor is used to take this into account. When an equivalent dose to an organ is multiplied by the tissue weighting factor for that organ the result is the effective dose to that organ. The unit of effective dose is the sievert (Sv).
If more than one organ is exposed then the effective dose, E, is the sum of the effective doses to all exposed organs.
Source (http://www.arpansa.gov.au/radiationprotection/basics/units.cfm)
So after reading around for a bit, my guess would be that if you knew how much radiation a person had been exposed too (by a fancy medical scanner) before they kicked the bucket and knew what the expected dosage rate was then you could guess the length of time they had been in space. But any sort of random radiation burst (like a solar flare) would probably make a dent in your data, also body size and clothing/shielding could impact it adversely.
(on another note... Also by looking at the source graph, you want to shield your nuts the most when going into a high radiation environment! :D)
Since something in space will only go in the direction that force imparted on it and until another force is imparted on it, a sophisticated enough program and a good knowledge of all nearby objects you could mathematically figure out where the body came from. Especially if you coupled it with your radiation guesstimate and superior knowledge of where all the local spacecraft were at the time.
That said, if you bumped into a frozen stiff that was eons old before it got burnt up in an atmosphere somewhere or a sun, the errors in the calculations may not be terribly helpful!
What about the air? Would breathing a higher or lower pressure of air, or even a different gas mixture affect decomposition? (Like when an astronaut needs to wear a low tech vacc suit and must breath a near pure oxygen mix because the pressure in the vacc suit is lower and has a different gas mixture than the spacecraft or station.)
By forensic examination of the lungs and hemoglobin in the blood, can you determine what the victim was breathing and at what pressure?
Hmm, there's a good question. Good enough to divert me from lecture prep and on to what happens to hemoglobin after death. That should teach me not to browse theRPGsite with PubMed open in another tab ;)
Anyway, the long and the short of it is that oxygen gets depleted from a dead body's blood. Deaths by cold exposure, and immediate deaths by traumatic injury (e.g. near instant exsanguination, massive head trauma), tend to preserve postmortem blood oxygen levels (measured by oxyhemoglobin/total hemoglobin ratio), but just about everythimng else, from outright asphyixia or drowning to "natural causes", will deplete blood oxygen, regardless of pre-death atmospheric levels, in minutes to hours.
As far as I can tell, I don't think blood gas analysis can reveal distinct pressures or different proportions in gas mixtures, if we're talking about inert gases like nitrogen or carbon dioxide. Toxic gases may create stable hemoglobin compounds such as methemoglobin (several toxic agents and a few rare diseases), carboxyhemoglobin (carbon monoxide) or cyanohemoglobin (cyanide) which may be detected on postmortem biochemistry (if and only if you know what you're looking for).
Decomposition relies on oxygen only for a short while. The classic forensic signs of decomposition mostly rely on anaerobic bacteria, originating from the gut, and oxygen levels at death will be irrelevant. However, if you store the corpse inside a sealed environment with very high oxygen concentration, you may slow down (but not prevent) decomposition.
More than a bit of guesswork above, but I hope that helps.
Quote from: The Butcher;654262Hmm, there's a good question. Good enough to divert me from lecture prep and on to what happens to hemoglobin after death. That should teach me not to browse theRPGsite with PubMed open in another tab ;)
Victory is mine! :D
Quote from: The Butcher;654262Decomposition relies on oxygen only for a short while. The classic forensic signs of decomposition mostly rely on anaerobic bacteria, originating from the gut, and oxygen levels at death will be irrelevant. However, if you store the corpse inside a sealed environment with very high oxygen concentration, you may slow down (but not prevent) decomposition.
More than a bit of guesswork above, but I hope that helps.
Oh, that is beautiful! Imagine finding a corpse of an astronaut in a vacc suit that used 100% oxygen at low pressure as its life support gases. The rate of decay (? decomposition) of the body would be skewed so that a definitive time of death would not be known (Unless the culture has had space travel for awhile, long enough to develop a database of how bosies decompose in these circumstances).
Quote from: jeff37923;654361Oh, that is beautiful! Imagine finding a corpse of an astronaut in a vacc suit that used 100% oxygen at low pressure as its life support gases. The rate of decay (? decomposition) of the body would be skewed so that a definitive time of death would not be known (Unless the culture has had space travel for awhile, long enough to develop a database of how bosies decompose in these circumstances).
Actually, absolute oxygen pressure would be more important than the oxygen content of the gas mixture in inhibiting anaerobic bacterial metabolism (this is how hyperbaric oxygen therapy chambers work). So maybe if you're murdering someone and want to throw off investigators, you might tamper with the life support settings and increase pressure in the craft (or maybe even inside the suit).
You could even kill your mark with a rapid increase in pressure inside the suit (probably by tension pneumothorax caused by pulmonary barotrauma), leave the corpse inside, and make it seem like an accident.
In any case, I didn't find a lot of hard information on those things, but Google got me this neat little text (http://space.about.com/cs/basics/a/bodyvacuum1.htm) about what dying of vacuum exposure probably looks like.
Undersea operations are way worse then space for pressure. Since the normal pressure we are exposed to is ~1 atm, our body only "pushes out" at 1 atm, not enough to blow up. Go down to a deepsea diving rig where the pressure is at 8 atm and their bodies have equalized, then go to 1 atm through rapid depressurization - kablammo, Outland style body explosions. Check out the Byford Dolphin incident.