Behind The Tape
Wednesday, December 23 2009
Grrreetings Class! Today we will talk about rigor mortis. It's the reason bodies are often referred to as "stiffs!" Since this is Kindergarten Crime Scene, we won't go into all the chemical reasons behind why the body turns stiff after death. In a nutshell, when your body stops breathing, your cells no longer receive oxygen. Without oxygen, the cells get a build-up of calcium ions, causing the muscles to stiffen. This continues until the muscle proteins start to break down during decomposition.
Even that explanantion is a bit complicated. Sooo . . . . to make it even simpler. When you die, you stop breathing and start to stiffen up. This stiffening is gradual. It takes a while. The stiffening isn't permanent either. There are a LOT of factors which affect rigor mortis, but in general, we say 12 hours in, 12 hours out. (And now that I've told you that, I'll tell you why it isn't true!)
Temperature affects it. You stiffen faster and go out of rigor faster in warmer temperatures. Cold temperatures slow it down. Physical exertion prior to death speeds it up. If you were jogging and dropped dead, you'd stiffen up a lot faster. It also happens faster in folks with low muscle mass, like old people or children. It happens more slowly in fat people. There are MANY factors to consider when using rigor mortis to determine how long a body has been dead.
There's also a pattern to the process of rigor mortis. The stiffening tends to take place in the smaller muscles in the upper part of the body first, and then travel down the body. That means the face and head. It becomes noticable first in the eyes, mouth, and jaw. (This is why they used to put coins in the eyes of the deceased to keep them closed!) The process proceeds for 12 to 18 hours until the body is literally "stiff as a board." Then it gradually goes away. The muscle proteins break down and the body loosens up again.
Now, how does that affect my job?
Like post mortem lividity, rigor mortis is a good way of telling me if my body has been moved. Rigor mortis DOES give you a pretty accurate picture of the POSITION of the body when it stiffened up. If I come in the room, and Grandpa is lying on his back with his arms in the air, I'm gonna assume that someone moved Grandpa. If Grandpa is stiff as a board, and you tell me he was watching Oprah in the recliner just two hours ago, it's gonna raise my eyebrows a little.
When considering the factors that affect it, rigor mortis still gives a "rough" time of death (really rough). Although I don't put a lot of emphasis on it, rigor mortis is still something to consider when you look at a crime scene.
Rigor is definitely something to consider when you have to bury large farm animals like horses or cows because it determines how big the hole has to be. I've heard horror stories about friends having to break legs (it makes me shudder inside). It grosses me out and I won't go into detail. I'm sure you get the picture. Because I know that rigor mortis is a natural state of decomposition, I accept that I will have to deal with this when putting down large farm animals. Because there is often a delay between the time you must put them down and the time you can get a backhoe out to the farm, things are a lot easier for everyone if you don't try to fight biology. Use some hay string to tie legs in a fetal position when the body is still flexible (just until you get them in the hole). To some folks it doesn't matter, but to me, an old horse is an old friend, and I will treat accordingly.
Okay, enough of that! To conclude, like post mortem lividity (also called livor mortis!), rigor mortis is a natural state of decomposition and a useful tool at crime scenes.
Posted by: forensicfarmgirl AT 09:01 am | Permalink | 0 Comments | Email