In a murder investigation, establishing a time of death help can lead to arresting and convicting the perpetrator — or exonerating someone wrongfully accused. That's why getting it right can mean life or death for someone likeTexas death row inmate Larry Swearingen. He is facing execution Wednesday for a murder he says he didn’t commit.
The science of “time of death” is something studied every day at the Forensic Anthropology Center in San Marcos, also known as “The Body Ranch.”
Scattered around an open field under the hot Texas sun there are a dozen human bodies. Their skin is blackened. Their flesh is half-eaten by bugs and varmints. They are in varying states of decay. This isn’t the scene from a horror movie or a mass murder — this is science.
“What we're interested in doing is getting some kind of idea of the rate of composition and then the pattern of decomposition,” said Daniel Wescott, the center’s director and professor of anthropology at Texas State University. “We typically have about 60 to 70 bodies out at at any given time that might be involved in various different experiments.”
This is one of the seven outdoor body composition laboratories in the United States and the largest such forensics research facility in the world.
“So what you want to try to do is have some kind of baseline information about what's going on and then alter a single thing to look at how that affects it,” Wescott said.
Here, human cadavers are left out in the open and carefully monitored for patterns of human body decomposition. That data is used to train forensic experts so when they look at a murder victim they can read the body and the crime scene to gain an understanding of the time of death.
“It's not guesswork,” Wescott said. “We do lots of bodies, so we have a good idea of the normal variation.”
In the murder of Melissa Trotter, establishing when she died is central to the conviction and the pending execution of Larry Swearingen. Trotter went missing in Willis Texas on Dec. 8, 1998. Her body was found 25 days later on Jan. 2 in the Sam Houston National Forest. She had been sexually assaulted and strangled. Her body was tossed onto a pile of bushes. Swearingen had been arrested and jailed on Dec. 11 — three days after Trotter was last seen alive.
Swearingen maintained he didn’t kill her, and, based on the condition of Trotter’s body, forensic experts have said there are questions about his guilt.
“The climate, weather, temperature, the data where the body was found, the environment where it was found,” Swearingen said. “[The forensic doctors] looked at all the weights, the organs — [they] looked at everything, and they said Melissa died within 10 to 12 days of her body being discovered.”
There is a lot of circumstantial evidence in this case that the prosecution says points directly at Swearingen but there is no DNA that ties Swearingen to the death of Trotter. The prosecution’s case depends on establishing that Trotter died before Swearingen was jailed. The forensic evidence for that narrative is weak at best.
“Every doctor has said from Texas and beyond that Melissa was dead no more 10 to 12 days before discovery, which would have put it at about the 18th [of December], and I had been locked up over a week by that time,” Swearingen said.
Kelly Blackburn is with the Montgomery County District Attorney’s Office, which prosecuted Swearingen. He said one piece of evidence isn’t what this case is about.
“Science can only tell you so much,” Blackburn said. “You have to look at the whole story because no matter how good the scientist is, no matter how unbiased they claim to be, there is still interpretation.”
And what the conditions were in the Sam Houston National Forest for those 25 days is also undetermined.
“If you're looking at what the weather was like at Intercontinental Airport and basing the way the body would decompose on those weather patterns versus what's actually happening 20 miles north of here in the national forest, and how cold the temperature could have gotten during that period of time, and how cold it stayed for that period of time, all of that comes into play,” Blackburn said.
James Rytting, Swearingen’s attorney, said the time of death is a major problem for the state’s case. He said the bottom line is that when Melissa Trotter’s body was discovered, if it had been out in the woods for 25 days, it would have been in terrible condition.
“The day that girl disappeared as it did on the slab and it was left out in the open in the Texas woods. It is, as everyone knows, filled with vultures, with raccoons, with wild pigs. There should not have been much left to that body at all. After 25 days, let alone 105 pounds out of 105 pounds,” Rytting said.
But Wescott from the Body Ranch said some bodies don’t always decompose the way you’d expect them to — sometimes there are surprises.
“So typically when we get one that is a little bit off of what we expect, it usually turns out to be that they were on heavy dose of antibiotics at the time or sometimes chemotherapy,” Wescott said.
Forensic entomology and establishing time of death is a science — but if it’s an exact science, it shouldn’t depend on if it’s being used by the prosecution or the defense.
Editor’s Note: This is the second story in a three part series that investigates Swearingen’s claim that he’s innocent.
David Martin Davies can be reached at dmdavies@tpr.org or on Twitter @DavidMartinDavi
