In article ,
says...
I'm trying to write a story and I would like to know if there would be a
difference discernable under Post Mortem between someone who died in a space
station and was exposed to vacum to someone who died due to vacum.

Alive and exposed to vacuum the heart is still beating and blood still
flowing through the lungs. Gasses bound to hemoglobin (O2, C02, CO - if
there's any around) and dissolved in the plasma (N2, everything else)
would outgas rapidly through the lungs. This would leave little in the
blood and would be the actual cause of death.

Dead and exposed to vacuum the blood wouldn't be moving through the
lungs. Blood far from the lungs would retain these gasses for some time.
How long I can't say, but all else being equal, the exposed dead guy
would have higher for blood gasses than the exposed alive guy.

Then of course there's all the evidence left by what actually killed
him.

Marc