How does forensic know how long a body has been dead?

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I’ve always been curious on how they know how long a body has been dead for? For example, if they say “the body has been dead for 2 hours”, how come it’s not 2 days, weeks, etc..?

edit: spelling

In: Biology

After a while the biomolecules start to oxidise and fall apart. I believe they can chemically work out the approximate length a body has been dead for based on how oxidised the biochemicals are.

The body goes through changes over time. In a short period you can tell based on the body itself, over longer time you can tell roughly based on things like how old larvae eating the body are and stuff like that. As it’s longer, it’s harder to get an exact time

Different things happen to a body depending on how long it’s been dead. Blood stops circulating and starts pooling in certain areas. Muscles get rigid. Temperature drops. Skin dries out. After a while, bacteria in the gut cause inflation of the gut, stomach content starts digesting itself, cells deprived of oxygen and nutrients die and start falling apart. Certain insects lay eggs in favorable environment. Etc etc etc; these things happen predictably and relatively consistently, depending on the environment.

In most cases, if you’ve reached rigor Mortis, that usually lasts like 48 hours? Starting around hour 4 of death. You can’t really tell down to the exact minute when someone has died. Especially if you’re basing it off rigor mortis. Sine that lasts almost 2 days. Then other things happen after, and so on. Its basically just a guess, based on where the body is at in decomposition. But could be days off the actual time of death.

Edit: you should look up ‘ask a mortician’ on YouTube. Shes very informative.

this a an awesome subject, and there are so any ways, like what parts have decomposed, or muscle rigidity, or blood pooling, but one of my favorites is bugs. they can see the maggots or the flyes on the body and tell how land they’ve been dead with the age of the maggots.