Rigor Mortis

A body goes stiff when it has no life. This is known as rigor mortis. The body goes stiff in the same position that it was in when it died, and moving the limbs may be difficult and must be done with care.

How does rigor mortis happen? When we breathe in, we take in oxygen. Most of the oxygen we inhale is used to form ATPs (adenosine triphosphate) in the mitochondria of the cell. ATPs are used for energy, movement, activities, etc. The ATPs mainly prevent the actin and myosin from sticking together when the muscles contract. This may be a little confusing if you don't know about actin in myosin. The contraction and relaxation of the actin and myosin are what cause our muscles to move.

Rigor mortis happens because we stop breathing in oxygen when we die, so ATPs cannot be produced to prevent the actin and myosin from keeping fixed positions. However, rigor mortis does not last; a body does not stay stiff for long. Autolysis takes place and the body starts to self digest. The cells of a human body contain lysosomes, which are biological enzymes used to destroy unwanted substances by digesting them. Lysosomes can digest just about anything. When a person dies, his cells burst and the contents flow out. This gives the lysosomes the liberty to digest the entire body. Rigor mortis ends at this point because autolysis takes place and the tissues seem to 'soften' as the body further decomposes.

Forensic pathologists can also make use of rigor mortis by determining the time of death and whether or not a body has been moved.

Livor Mortis

Livor mortis is the effect of gravity on the non-circulating blood in a cadaver (corpse.) When a person dies, his heart stops beating, and when the heart stops beating, the blood stops circulating around the body. The heart acts as pump to get the oxygenated blood in all the organs, when it stops, can you imagine what the blood is like the corpse? It also stops moving. And so, the blood starts to move towards the ground under the effect of the gravitational force. Whichever way the body is facing, if it is lying on its back perhaps when it died, the blood will accumulate in the part closest to the ground, giving it a reddish-purple almost bruise-like appearance.

In the past, it was thought that the darkening color of the skin due to the accumulating blood were bruises.Now that we know better, we also know that if the part of the body that the blood is accumulating in is in contact with an object, that part of the body that is in contact with something won't get darker in color. This is because the capillaries are compressed and the blood cannot accumulate in those areas.

Livor mortis is very important in criminal investigations because it helps us know if the body has been moved after it has been killed. Livor mortis usually occurs within 3 hours after the person has died. If the person died facing down, then the blood accumulation would be towards the stomach. If the body has been moved and was placed facing another direction, then forensic investigators can tell that the body was originally facing down and has been moved. 

The Three Stages Of Death

After a person dies, the body undergoes three different stages. Each stage happens gradually and after the previous one. Pathologists can determine the time of death of a person by examining the dead body. Usually, if it is in one of the first stages, then the body hasn't been dead for long. Let's discuss these stages.

Dead bodies are known as corpses, but the more medical term for a human dead body is a cadaver, or sometimes carcass (although 'carcass' is mostly used to describe and animal's corpse, and not a human's). Autolysis is the first stage of death, it is more commonly referred to as self-digestion. When a person dies, the body begins to digest itself using its digestive enzymes (enzymes are biological catalysts used to speed up chemical reactions in the body.) But how do investigators know when a body has begun autolysis? As a result of this process, liquid is formed between the layers of the body which causes the skin to 'peel' off. This is the stage that flies start to gather on the openings of the body to lay eggs, the maggots are hatched in the corpse and they start to eat the body when they get under the skin.

1 week after the body has been dead, bloating occurs. By 'bloating', I mean the body begins to 'puff up'. This is due to accumulating gases in the body. It is most notable in the abdomen of the person. The increase of air pressure of the accumulating gases forces liquids out of the openings of the body (nose, mouth, etc.) and this is what usually causes the stench of a dead person. 

Putrification is the last and final stage. It also takes the longest time. This is the stage where the organs of the body liquefy and become unidentifiable. It takes several years for the completion of this process until all that remains is the skeleton.

Luminol

Luminol is a chemical used by scientists to detect the presence of blood in a crime scene. Even when there appears to be no signs of blood, luminol will exhibit a chemiluminescence with as little as a few hundred red blood cells. So if crime scene has been 'cleaned up' you will get a blue glow wherever there is blood.

The chemical formula for luminol is C₈H₇N₃O₂.

How does it work? It reacts with iron that is present in haemoglobin. Haemoglobin is a globular protein that carries oxygen in red blood cells. Therefore, if haemoglobin is present, the luminol will react with the iron it contains and 'glow'. Luminol requires the presence of an oxidant in order for it to be activated, something like hydrogen peroxide (that's H2O2.) We use a catalyst, usually iron, to speed up the reaction. The hydrogen peroxide decomposes to form oxygen and water.

How long does the luminescence last? Roughly 20-30 minutes. It's pretty cool actually, and it doesn't need to last long, forensic investigators capture the images of the scene with special cameras, so they don't even need it to last.

First Post

Hi! I'm Clementine and this is my new blog. I'm studying O levels at an international school in Malaysia and it's my dream to study in the medical field of forensic science and become a pathologist. This blog is going to be all about interesting facts about forensic science and criminal investigations, since people are tired of lending me their ears for these things. I hope my blog turns out to be a success, I'm just going to write about what I like.