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How Is Time of Death Determined for a Crime-Scene Victim? Hint: It Usually Involves Bugs

The coroner's office removes a body
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    How Is Time of Death Determined for a Crime-Scene Victim? Hint: It Usually Involves Bugs

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      Adam Janos

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      How Is Time of Death Determined for a Crime-Scene Victim? Hint: It Usually Involves Bugs

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      March 29, 2020

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      A+E Networks

When Whitney Houston’s body was found at the Beverly Hilton Hotel on the afternoon of February 11, 2012, she was still recently deceased. So it should have been easy for the medical examiner to determine her time of death.

If only she hadn’t been submerged in a bath, complicating everything.

For investigators coming across a fresh corpse, one of their most important jobs when arriving at the crime scene is to narrow the window for time of death as much as possible. That way, detectives can begin looking in earnest at the crime itself: cross-referencing witness statements and alibis to better zero in on suspects.

But ascertaining time of death is easier said than done.

Body temperature drops

According to Lawrence Kobilinsky, a forensic scientist and professor at John Jay College of Criminal Justice, time of death on a fresh corpse can best be ascertained via a measurement of core temperature.

“It’s not linear,” Kobilinsky cautions. Still, he says, “most examiners use a formula to…come up with an approximate range.”

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For that formula to work best, a freshly discovered body’s temperature is taken rectally. For the first several hours after one’s heart has stopped beating, the body’s core temperature drops towards ambient temperature (i.e. room temperature, if indoors). The formula approximates that the body loses 1.5 degrees Fahrenheit per hour, so the rectal temperature is subtracted from the normal body temperature of 98 degrees. The difference between the two is divided by 1.5, and that final number is used to approximate the time since death.

Of course that simple formula only works if several factors are assumed constant: that the ambient temperature hasn’t changed since the death… or that the victim was discovered clothed and in the air rather than in, say, a bathtub full of water. But according to Nathan Lents, a forensic biologist colleague of Kobilinsky at John Jay, things are rarely so simple.

“A body in the field—rarely are you so lucky that it’s 72 degrees all day and all night long,” he says.

In a climate-controlled environment, it will take six or seven hours for a body to reach ambient temperature. Further biological evidence taken in conjunction with core temperature helps better fill out the picture.

Blood starts to pool

One of those factors is livor mortis. Once the heart stops beating, blood stops circulating and responds instead to gravity, pooling into the parts of the body closest to the ground. This causes marbleized discoloration of the body. Livor mortis generally begins 20 to 30 minutes after the heart stops beating, but passes through stages. Between 30 minutes after death and approximately one hour, for example, the skin will “blanch” when pushed, with blood leaving the area where pressure is applied. After that, once livor mortis has fully set in, blanching ends.

In addition to helping with time of death, livor mortis can also show investigators that the body has been moved if the markings of livor mortis don’t correspond with the position the body is in.

Becoming a stiff

About three to six hours after death, rigor mortis begins to affect the corpse. Muscles lock into place, beginning with small muscles in the head, the eyelids and the jaw, before moving on to fingertips, neck and then larger muscles. Rigor mortis sets for 18 to 36 hours before dissipating.

Once livor mortis, rigor mortis and ambient temperature are all in place, determining a precise window of death becomes trickier.

Tell-tale bugs

“From 10 to 50 hours [after death], it’s basically a wild guess,” says Lents. That’s why forensic entomologists—who study the insects that accompany decomposition—are so important. After the first several hours, bodies begin to decay at different rates, depending on a myriad of factors, including the prior health of the victim.

Forensic entomologists look at which critters have been feeding on the dead, and for how long. If they can determine a time when insect colonization occurred, it can help them infer time of death.

The first bugs attracted to a dead body? Blowflies, says Lauren Weidner, a forensic entomologist and lecturer at Purdue University. If they have easy access to a body (i.e. outdoors or with an open window, in agreeable weather, during the daytime), Weidner says “insects can arrive within minutes and then colonize within the hour.” The blowflies will lay tiny eggs in batches, usually in orifices or in a wound. After 15 to 26 hours, the eggs hatch into tiny maggots that feed for days.

By the fourth day, the maggots will migrate and enter cocoon-like pupae in dry areas away from the body, which is still wet and thus attracts other insects that might prey on the vulnerable pupae. From the pupae come the next cycle of blowflies. By measuring where the blowflies are in this life cycle (e.g. the approximate age of a feeding maggot), forensic entomologists can work backward to determine the minimum time since colonization—and thus death.

Then comes bloat

Once the body reaches the bloating stage, the critters consuming the body change again.

“That would be four to five days on nice warm summer days,” says Lents. “By then your margin of error is measured in days—even [a] couple of days.” The body bloats as a byproduct of bacterial activity in the organs, leading to an accumulation of gases. Lents is researching how measuring skin bacteria can help investigators get narrow windows weeks after death. Others have homed in on bacteria in the small intestine.

“I’ve used bacteria to get a two-day window, out to about six weeks,” he says. “You’re pretty deep into decomposition by that point.” As of yet, study of bloat-related bacteria isn’t far enough along to be used in investigations, but Lents is optimistic that that will change soon.

Once the body has reached the bloat stage, the succession of insect begins to show hints. In bloat, blowflies will leave and house flies begin to colonize. Dermestid beetles (also known as skin beetles) will arrive at the body later still, once it has begun to dry out.

By that point, the body has been dead for weeks, going on months.

“Sometimes museums use [the beetles] to clean bones,” Weidner explains. Still, she says, even after a body is picked clean, forensic entomologists can still be of use. That’s because different insects are present in different geographic areas depending on the time of year. Investigators can glean information by looking at the corpses of the flies themselves: If the flies that fed, pupated and hatched in the room are only in the area in the summer, then it’s reasonable to assume that the body died in the summer.

“If insects were there,” Weidner says, “then entomologists can be relevant.”

(Image: Photo by Barbara Davidson/Los Angeles Times via Getty Images)

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