One of our favorite research books is Criminal Investigation by Dr. John Macdonald and Lieutenant Tom Haney, former commander of the Homicide/Assault unit of the Denver Police Department.
In Criminal Investigation, a seasoned homicide detective, Joe Russell, speaks about the simplicity of homicides:
Homicides are simple; don’t make them hard. It’s seldom an insurance fraud with a hired killer. There are few Mafia killings. They leave their mark, they throw the gun. They know it’s clean, it can’t be traced. Drug killings will be hard to solve [because] you’re working with a criminal element. Most homicides are within the family, within friends. Keep it simple, look at the people the victim knows. It’s family or friends.
I get upset when I see detectives leave the crime scene and say, ‘I don’t know what happened.’ You’ve got to read the crime scene. You should stay there until you figure it out.
[For example] There was a body of a woman in the hallway by the stairs in an apartment house. People there said someone from upstairs or downstairs must have dumped the body there. She had not been dragged and her body was too heavy to have been carried upstairs or downstairs. She must have been killed by someone in one of the two apartments on that floor. There was an old man in one apartment, and he would not have been able to carry the body. In the other apartment was a young man who was known for picking up girls. He was the one.
Time of Death
Just as private investigations are both an art and a science, so is predicting the time of death, which requires both technique and observation to make an estimate. The sooner after death a body is examined, the more accurate this estimate will be.
Time of death does more than tell when someone was killed. It can also predict how far the suspect might have traveled after the killing, or it can tell where the victim might have last been seen alive. Your fictional PI will always look at this sometimes inexact calculation. Factors used to estimate time of death include the following indicators.
Lividity
When the heart stops beating, the blood stops flowing and is then pulled by gravity to the lowest parts of the body where it discolors the skin. This red/purple discoloration is called lividity, which is usually perceptible one-half to two hours after death and reaches its maximum by eight to twelve hours.
Note for writers: Within the first six to eight hours after death, this discoloration can shift along with the body being placed in a different position. But after that, the discoloration becomes fixed and further moving the body will not change its lividity.
Lividity usually has a cherry red color in carbon monoxide poisoning, cyanide poisoning and when the body is refrigerated/exposed to low temperatures.
If lividity shows in the upper surfaces of a victim’s body, the body has been moved. Proving movements after death can help disprove a suspect’s statements.
Rigor Mortis
Soon after death, the body begins to stiffen, which is called rigor mortis and is due to chemical reactions within the muscle cells. Typically, this can be detected first in the small muscles of the face, neck and hands before progressing to the larger muscles.
Rigor mortis is an unreliable indicator of the time of death because so many factors affect its onset, duration and disappearance. Usually it begins within two hours after death and becomes perceptible within four hours. Generally, a body becomes fully rigid around twelve hours after death before the process begins to reverse itself, with rigidity loss beginning again with the smaller muscles before the larger ones. This is referred to as the flaccid stage of rigor mortis.
Prolonged muscular activity right before death hastens the onset and disappearance, as well as electrocution and heat (from disease/climate). It then disappears when body decomposition begins.
When death occurs during great emotional tension, particular muscles (such as the hand holding a gun) or the entire body can be frozen in position at the moment of death.
Rigor mortis can tell a story about the crime. For example, if parts of an otherwise stiffened body are in an illogical position as they relate to the rest of the body (for example, a body lying on a sidewalk has a raised hand), then the body was most likely moved twelve to thirty-six hours after death.
Body Temperature
One formula for estimating the time of death is:
Normal body temperature – rectal temperature / 5 = number of hours since death
Another calculation is that, under normal circumstances, a corpse loses body heat at a rate of approximately 1.5 degrees per hour.
Of course, such calculations have limitations as many things can affect body temperature: cocaine (other accelerant drugs), strangling, hanging, brain hemorrhage, exercise and fever all raise the body’s temperature. Warm surroundings, clothing, bedding and extra body fat delay the rate of cooling. Exposure to cold lowers the body’s temperature, both before and after death. Also, environmental temperature may change, due to such things as nighttime and wind chill, thereby affecting the body’s temperature.
Ultimately, the corpse will lose or gain heat until it stabilizes with its environment.
Stomach Contents
The following descriptions of the digestive tract can provide clues about a decedent’s activities, psychological state, whereabouts and time frame prior to death:
- Empty stomach=death probably occurred at least four hours after the last meal.
- Small intestines empty=Death probably occurred at least twelve hours after the last meal.
- Small meal=Gone from stomach within one or two hours.
- Large meal=Gone usually after five hours.
- Gastric contents may tell what the subject has eaten, which may provide a clue to where he/she ate.
- Stress stops digestion.
- Other factors affecting digestion: Drugs, alcohol, disease, type of food.
Vitreous potassium
Post death, the potassium level rises in the vitreous humor, which is the watery fluid in the eyeball between the retina and the lens. There are tests that detect the time of death based on this potassium level. Errors of up to 10 hours are possible when the test is done within 24 hours, with increasing rates after that.
Decomposition
The following shows the general stages of the corpse’s decay process:
- One to five days after death: greenish discoloration of the skin of the lower abdomen, followed by in order of occurrence:
- Purple, red, blue discoloration over the body
- Bloated face, distended body
- Blisters/vesicles appear on the skin (as body swells, it smells)
- Bloodstained fluid from orifices.
Insect infestation
In warm to hot weather, it takes only a few seconds for the first flies (blow flies) to land on a dead body outside in a wooded area. Other insects include ants and beetles. Maggots hatch from fly eggs in 18-24 hours. Entomologists studying the eggs, larvae, pupae and so forth may be able to determine time of death.
