From Scott:

A commonly asked question, both at real crime scenes and at those from the world of fiction, is this: how long has the victim been dead? A variety of tools is available to investigators who are looking to answer that very question. However, sometimes the methods described by fiction authors fall short of reality. Let’s take a look at some ways we can get to the truth on this matter. Keep in mind that many of these methods are affected by temperature. The warmer the air, the faster all of these processes of decomposition will become.

One simple manner is by examining cell phones and other technology used for communication. This is a method I just used in the past week on a real case. A one-car, one-occupant accident occurred on a rural road, killing the driver. However, the wreckage wasn’t discovered for some time, so we had no idea how long the person had been deceased. We can download data from the Airbag Control Module (a.k.a. the “black box”), and while this will certainly tell us about the crash, the data doesn’t include a date and time stamp.

Instead, I checked her cell phone. By looking at her outgoing calls and text messages, along with her access to social media such as Facebook, I was able to determine that she was still alive at 1 a.m. She was found at around 3:00 a.m., so the time of death is down to a two-hour window. Not bad. If this had been a homicide, we’d have a great starting point for checking the alibis of potential suspects.

While I’m on the subject of suspects, let me take a moment to go over more police terminology issues. I’ve been a cop for almost sixteen years, and I’ve never heard a cop refer to a suspect as a “perp” (short for perpetrator), or a victim as a “vic.” As far as I can tell, this is a television construct.

Another TV and movie plot device I’ve seen is having an investigator jab a thermometer into the victim’s body to get a liver temperature. Aside from the issue of the damage that would cause to the body (thus disrupting the accuracy of an autopsy), body temperature is not an accurate measure of time of death. Too many factors come into play for how soon a person will “assume room temperature.” Air temperature, humidity, indoors versus outdoors, wind, and ground/floor temperature all affect the rate of cooling once the victim dies. I’ve never seen anyone jab a thermometer into a body to determine time of death.

One interesting area of forensic investigation is forensic entomology, the use of insect activity to determine a time range for someone’s death. At the scene, the investigator would collect samples of flies and maggots from on and around the body. The temperature of the maggot mass is also taken (maggots are baby flies, and they tend to clump together into a large mass, like a scoop of rice). A forensic entomologist can use this to calculate the number of generations of flies that are present, which will then indicate an approximate time of death, give or take a couple of hours.

Lividity, or livor mortis, is a purplish discoloration of the skin that results from the pooling of blood in the capillaries, after the heart stops beating. This color will be absent in the points where the weight of the body is the most pressed against the floor. So if a corpse is left on its back, the skin covering the points of the shoulder blades would be white, while the rest of the skin on the back would have lividity. The blood is squeezed out of the capillaries in these areas, preventing the forming of lividity.

Depending upon ambient temperature, the discoloration will begin to form anywhere from twenty minutes to three hours after death. The color has usually peaked six to twelve hours after death. Not only does this give a general idea about the time of death, but it also helps with determining the nature of the death. If the location of the lividity isn’t consistent with the position of the body, we know the body was moved sometime after death.

Rigor mortis (or just “rigor” for short) is a stiffening of the muscles resulting from the early stages of the decomposition process. Like lividity, the timing of the onset depends upon the temperature around the body. Typically, rigor starts about three hours after death. By twelve hours, the effect has peaked, and it has become extremely difficult to manipulate the limbs. After about three days, the effects of rigor will be gone. So if your character finds a body five days after the murder, describing the body as being “stiff” would be incorrect.

But what can be done to gauge the time of death over longer periods of time? One way is the odor. Within a couple of days, the body will produce a strong, offensive odor. The best way I can describe it for the uninitiated is imagine the worst case of athlete’s foot you can possibly think of. Then make that smell about ten times worse. The death odor is more noticeable when the body is moved. However, after five or six days, the odor will be potent even before the body is moved.

Other things begin to happen after about a week. The skin will blister and begin to slip off, referred to as “slippage.” New discoloration will appear, green and black in color, accompanied by a significant increase in the potency of the odor. Insects will attack every orifice they can get to: eyes, ears, nose, mouth, and genitals. After several days of heavy insect activity, the amount of flesh they’ve eaten will be obvious. In a case I had last summer, after only three weeks (in a very hot house) the flies had reduced the deceased person’s head and right arm to little more than bone.

A final note for this installment: The odor encountered at death scenes can be overpowering, and it tends to nauseate people the first few times they encounter it. Some people will vomit, and some will not. The best way I’ve found to deal with it is to wipe Vick’s salve under my nostrils, just like they do in the movies. I’ve heard some people say that this would make the smell worse, because it tends to open your sinuses. But in my experience, the smell of Vick’s overwhelms the death odor, making a horrid scene bearable.

More to come in the next installment!

–Scott