Q: Is possible or likely for blood alcohol levels to increase or decrease in a decomposing body, and if so during what stages of decomposition?
A: Alcohol is usually consumed in the decay process but may actually be produced and this might cloud any toxicological examinations on the corpse. Make it look as if the victim consumed more alcohol than he actually did.
I must point out that alcohol is not commonly produced but it does happen. The alcohol is a byproduct of the action of some types of bacteria that are involved in the decay process. This means that alcohol can only appear during active decay. What is that time period? A little about putrefaction.
The decomposition of the human body involves two distinct processes: autolysis and putrefaction.
Autolysis is basically a process of self-digestion. After death, the enzymes within the body’s cells begin the chemical breakdown of the cells and tissues. As with most chemical reactions the process is hastened by heat and slowed by cold.
Putrefaction is the bacteria-mediated destruction of the body’s tissues. It is this decay that might cause alcohol formation. Not always, but sometimes. The responsible bacteria mostly come for the intestinal tract of the deceased, though environmental bacteria and yeasts contribute in many situations. Bacteria thrive in warm, moist environments and become sluggish in colder climes. Freezing will stop their activities completely. A frozen body will not undergo putrefaction until it thaws.
Under normal temperate conditions, putrefaction follows a known sequence. During the first 24 hours, the abdomen takes on a greenish discoloration, which spreads to the neck, shoulders, and head. Bloating follows. This is due to the accumulation of gas, a byproduct of the action of bacteria, within the body’s cavities and skin. This swelling begins in the face where the features swell and the eyes and tongue protrude. The skin will then begin to “marble.” This is a web-like pattern of the blood vessels over the face, chest, abdomen, and extremities. This pattern is green-black in color and is due to the reaction of the blood’s hemoglobin with hydrogen sulfide. As gasses continue to accumulate, the abdomen swells and the skin begins to blister. Soon, skin and hair slippage occur and the fingernails begin to slough off. By this stage, the body has taken on a greenish-black color. The fluids of decomposition (purge fluid) will begin to drain from nose and mouth. This may look like bleeding from trauma, but is due to extensive breakdown of the body’s tissues.
The rate at which this process occurs is almost never “normal” because conditions surrounding the body are almost never “normal.” Both environmental and internal body conditions alter this process greatly. Obesity, excess clothing, a hot and humid environment, and the presence of sepsis (infection in the bloodstream) might speed this process so that 24 hours appear like 5 or 6 days have passed. Sepsis is particularly destructive to the body. Not only would an associated fever from the infection cause the body temperature to be higher at death, but also the septic process would have spread bacteria throughout the body. In this case, the decay process would begin quickly and in a widespread fashion. A septic body that is dead for only a few hours might appear as if it has been dead for several days.
As opposed to the above situations, a thin, unclothed corpse lying on a cold surface with a cool breeze would follow a much slower decomposition process. Very cold climes may slow the process so much that even after several months, the body appears as if it has been dead only a day or two. Freezing will protect the body from putrefaction if the body is frozen before the process begins. Once putrefaction sets in, even freezing the body may not prevent its eventual decay. If frozen quickly enough, the body might be preserved for years.
So, whether a particular corpse actually produces alcohol or not is unpredictable. How long it takes depends upon the conditions the corpse is exposed to. In a corpse in an enclosed garage in Houston in August, this process will be very rapid and the corpse will be severely decayed after 48 hours. If parked in a snow bank in Minnesota in February it might not even begin the decay process until April or May when the spring thaw occurs. And anything in between. The appearance of any alcohol would coincide with the time frame of the bacterial activity.
So how does the ME get around this possibility? How can he determine the actual alcohol level that was present prior to the decay process kicking in? He can’t with any absolute accuracy, but he does have a tool that will help him make a best guess. He can extract the vitreous humor from the victim’s eye—this is the jelly-like fluid that fills the eyeballs. The alcohol level within this fluid matches that of the blood with about a two-hour delay. That is, the level within the vitreous at any given time reflects the blood alcohol level that was present approximately two hours earlier. And the vitreous is slow to decay so it might be intact even though the corpse is severely decayed. By measuring the vitreous level the ME will know the blood alcohol level two hours prior to death and he can then estimate the blood alcohol level at the time of death.