Homicide Investigation Basics

May 29, 2015 Collins

Welcome to the third class, "Homicide Investigation Basics," based on course material that my husband and I taught four years ago to Kiss of Death, the suspense chapter of Romance Writers of America. I have updated and added content for this post.

In this third class, we cover the basics of homicide investigations -- think of it as Homicide 101. We review the key tasks conducted by law enforcement, including an overview about estimating time of death and types of wounds.

We do not provide any graphic images of crime scenes, although some might find parts of the written information, well, a bit grisly as we discuss things like what occurs in a body after death. Although far more unsavory detail can be found on the Internet, we wanted to advise our readers upfront.

Let's now kick off the class with...

When Police Are Called to a Homicide Scene

In general, when police respond to the scene of a homicide, they do the following:

Assess the physical condition (without compromising evidence) of the deceased and insure that emergency medical treatment is on the way.
Watch the scene carefully. Most homicides are unplanned crimes of passion and suspects don’t always have extra time to flee. The officer should look for getaway vehicles/persons hurrying from the area or behaving in a suspicious manner.
Search for surviving victims/suspects.
Protect the crime scene.
If a suspect lives in the same residence or has property rights, a detective will obtain a search warrant before further searching the area.
Obtain names and addresses of witnesses and other persons at the crime scene, license plates of nearby parked vehicles.
Note: If the victim’s car is missing, its description and license number would be obtained and broadcast to other police agencies.
Check neighboring homes for witnesses who heard or saw anything out of the ordinary.
Note: The sooner information is obtained from witnesses, the better. As time passes, especially in high-crime neighborhoods, they may become reluctant to talk.
If there are many witnesses, the key witnesses will most likely be transported to the police station for further questioning (there are more police officers and homicide detectives there and more facilities to keep witnesses separate—separating witnesses is always advisable so their stories aren’t tainted by what they overhear others saying). Meanwhile, statements will continue to be taken from other witnesses at the scene.
The detective in charge will do additional assessment of priorities: Should officers concentrate on an immediate search for a suspect? Should officers at an airport, bus terminal, or train station be alerted to watch for a suspect?
Photograph/videotape crime scene.
Detectives assigned to the case will make a quick determination of the victim and the scene to assess the motive for the killing.

Homicides Are Simple

US Army CID agents at crime scene (image is in public domain)

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.

Footwear impressions left at a crime scene (photo in public domain, photo attributed to Zalman992 on wikipedia).

Types of Wounds

We’ll briefly discuss some general types of wounds: shootings, stabbings and blunt force.

Shootings

At the scene of a shooting, a detective will look for:

The weapon (if can’t be found, detective will analyze the type of weapon and ammunition)
The location of the shooter, his distance from the victim, the direction of fire, his intentions/actions after the shooting. Many times certain marks on the skin can tell how close the weapon was to the victim when shot. Stippling and burn marks tell detectives that the shooter was proximate when the killing took place.
Clues (gunshot wounds, anything struck by bullets heading to and after hitting victim, spent bullets and casings, bloodstains, blood spatter and splatter, gunshot residue, witness observations).

Stabbings

Knife wounds occur in close encounters and usually leave a trail of blood. A cut or slash is longer than it is deep; a stab is deeper than it is long. A person who is dying as a result of exsanguination survives the killing wound much longer than one who is shot. Knife wounds reflect the condition of the blade. As a very general rule, cuts from a knife look smooth and straight whereas cuts resulting from blunt trauma are tattered and ragged.

Homicidal stab wounds are usually on the neck, left chest (as most people are right handed), back or abdomen. Defense wounds (on the palms, fingers and outer aspects of the forearms) point to homicide, indicating the victim tried to either grab the knife or to fend off the blows with his wrists, knuckles or forearms.

If the wounds are concentrated within a small region of the body, it may be that the victim was immobile at the time of assault (for example, held down, asleep or intoxicated). Many severe stab wounds suggest anger, sex homicide or psychosis.

Blunt Force

Attack by a blunt object (such as a revolver, iron bar, baseball bat, piece of wood) may leave its mark and may contain trace evidence.

Blunt force injuries may include abrasions, contusions and lacerations. Similar injuries result from being struck by a vehicle or falling.

Keep in mind that law enforcement has personnel, departments and equipment set up to handle homicide investigations. As mentioned earlier, information in this section is very high level and meant as an overview only. For more books on homicide investigations, check out PIstore.com.

This ends class 3. In the next class, which I'll post next week, we discuss why a PI might get involved with a homicide investigation.