rigor mortis

Rigor mortis is the stiffening of the muscles that happens 2-3 hours after a human or animal dies, beginning in the head and then it working its way down to the toes. After 12-18 hours, the body becomes completely stiff and the only way to move any of the joints is to force them, most likely breaking them. After 2 days, rigor mortis begins to wear off, once again starting in the head and then downward towards the toes. Once this process is finished, the body begins to decay, and eventually starts to decompose. Rigor mortis is very crucial in the criminal justice system and is used to provide clues and evidence in finding out information about someones death.

To explain it simply, rigor mortis is when a chemical reaction that causes the muscles to move in a living person, stops working once someone dies, and the muscles lock in place. Skeletal muscle fibers are made of myosin and actin filaments and when a muscle is used, nerve impulses trigger a biochemical reaction that causes them both to bond together, pulling the muscles filaments together, causing a muscle contraction. They stay contracted until a third molecule, ATP ( adenosine triphosphate), binds to myosin and releases it from actin. In order for our bodies to produce ATP, oxygen is required and therefore when someone dies, that oxygen supply is cut off, and the two filaments can not slide away from each other. They remain attached and the muscles remain contracted, or in other words, rigor mortis begins. This contraction is only ended once a process called autolysis kicks in, which is the self-digestion of body cells. The cell walls give away, its contents leak out and the muscles become weak and the body becomes flaccid and begins the next process of decomposition...

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...I do think that rigor mortis is very reliable in determining the time of death, although not an exact indicator. It is somewhat accurate in determining time of death and placement of body when the person died, although it should not be the only factor in the case. The results are just an approximation so it will not give the exact hour the person died, especially since there are so many other things that can effect the process of rigor mortis. It is helpful when someone has just died or within a few days, although if the person has been dead for weeks or more, investigating the persons state of rigor mortis is not useful. I learned in my research that hundreds of forensic science tools are needed in each investigation and can take years to put a crime scene puzzle together. Studying a bodies process of rigor mortis and lividity are the best first steps in doing so.