Want to know a simple observation that helps forensic scientists figure out A.) how long a body has been dead; and B.) if it's been tampered with? Serial killers: Please don't read the section below.
There are plenty of times when I weigh the fact that some stories are potentially hazardous with the fact that they're also quite interesting. This is one of those occasions. I can only comfort myself with the assumption that dedicated killers have probably already gleaned this information online. (And If they haven't, I would appreciate it if they cleared their browser history now.)
Sure, CSI is all lasers and interactive computer technology, but there are some simple things you can discover about a body literally poking around. For example, a corpse's paleness. It look like all the blood has drained away from the skin. Actually, all the blood has drained away from the top of the body. Corpses have pale faces because they are generally on their backs when and after they die. With the heart no longer circulating the blood, gravity causes the blood to pool in the body parts closest to the ground, reddening them.
The blood starts off as liquid, but after about twelve hours, it begins to congeal and forms permanent red and purple marks. This is called livor mortis — or post-mortem lividity — and they're responsible for the simplest test that can be used to determine the age of a dead body. If, when poking those marks, the area pales, the blood hasn't congealed and the body has been dead less than twelve hours. If the marks don't discolor, it's been over half a day since the person died.
So a dead body's back and thighs should be darkly marked, right? Again, that's not the case. When live flesh is pressed against an object, it pales too, because the blood is pushed out of the area. (This pallor is occasionally used to make sure that a finger used for fingerprint identification is living or dead.) Once the pressure is taken away, it darkens with a new rush of blood.
But a dead person never moves their body away from the pressure. The blood is kept out of those parts of the body pressed to the ground — that section of the body is pale while the blood congeals around it. If a person has been flipped on their stomach some time after they died, the pale marks, surrounded by congealed blood, would still mark how they originally lay. Indeed, if you're yearning to be the most handsome corpse around, be sure to die standing up.