For more than five weeks, a body lay undisturbed in a secluded Texas field. Then a frenzied flock of vultures descended on the corpse and reduced it to a skeleton within hours. But this is not a crime scene.

It was an important scientific experiment into the way human bodies decompose, and the findings are upending assumptions about decay that have been the basis of homicide cases for decades.

Investigators would normally have interpreted the condition of the bones as evidence that the woman had been dead for six months, possibly even a year or more. Now a study at Texas State University is calling into question many of the benchmarks detectives have long relied on.

The time of death is critical in any murder case. "If you say someone did it and you say it was at least a year, could it have been two weeks instead?" said Michelle Hamilton, an assistant professor at the school's forensic anthropology research facility. "It has larger implications than what we thought initially."

'It was stunning'

The study, conducted on 26 acres near the south-central Texas campus, stemmed from previous studies that used pigs, which decompose much like humans. Scientists set up a motion-sensing camera that captured vultures jumping on the body, breaking ribs, which investigators could misinterpret as trauma suffered during a beating. "It was stunning," assistant professor Kate Spradley said.

Researchers are monitoring a half-dozen other corpses, and they have a list of about 100 people prepared to donate their bodies to the project, which the school says is the first of its kind to study vultures.

The forensic center opened in 2008, as did a similar facility at Sam Houston State University in Huntsville, making Texas home to two of the nation's five "body farms." Forensic pathologists observe the decomposition process to see how corpses react to sun and shade, whether they decay differently on the surface or below ground and what sort of creatures are involved. Only in recent years has academic literature tried to establish formulas for death time based on stages of decomposition and environmental factors such as temperature conditions where the body was found.

The vulture research has drawn interest from homicide investigators, including Pam McInnis, president of the Southwestern Association of Forensic Scientists and director of the Pasadena Police Crime Lab in suburban Houston. She said the ability to account for vultures would "significantly" help investigators who already use insects to estimate time of death.

The body in the study was that of Patty Robinson, an Austin woman who died of breast cancer in 2009 at age 72. She donated her remains to research. Her son, James, said his mother would be delighted "if she could come back and see what she's been doing," he said. "All of us are pretty passionate about knowing the truth."

As for the research, "we're not a particularly squeamish lot," he added.

The project began after scientists noticed scavenger damage on other bodies even though the site was secured against animals. "It didn't fit the model of scavengers that we had seen before," Spradley said. "We realized we didn't account for something and it was vultures."

Mapping a predictive model

Vultures fly over much of the United States and are particularly abundant in the Southwest. Two of the most common species are turkey vultures and the more aggressive black vultures, which can exceed 2 feet in length with wingspans of 5 feet.

Spradley and Hamilton are working with state geographer Alberto Giordano to map the area where birds dragged bones. They hope to make a predictive model for police that will help determine time of death.

Sgt. Jim Huggins, a recently retired Texas Department of Public Safety criminal investigator who now teaches forensic science at Baylor University, said vultures were always something of a mystery for investigators. He said, "This is, as far as I'm concerned, it's cutting edge."