The medical examiner who autopsied the bodies of three women found at the Springfield home of accused serial rapist Stewart Weldon concluded they had been assaulted and killed, but could not identify a specific medical cause of their deaths.

Kayla Escalante, 27, America Lyden, 34, and Ernestine Ryans, 47, were all found during a police search of the home at 1333 Page Boulevard in May, following Weldon's arrest for the alleged kidnapping and rape of the mother of his children.

And the listed cause of each of their deaths was "homicidal violence," according to death certificates obtained by MassLive. The dates, times and locations of their injuries are unknown but were caused by assault, the certificates say.

Weldon was arraigned earlier this month for the murder of each woman, in addition to 49 other counts involving another eight living victims. He is accused of repeatedly abducting, raping and strangling women.

The bodies of Lyden, Escalante and Ryans were found in various states of decomposition, making it challenging for investigators to determine exactly how they died. Prosecutors wrote in the indictments that Ryans was killed sometime after Aug. 1, 2017, Lyden after March 1 of this year and Escalante after April 1.

The Hampden District Attorney's Office did not respond to a request for comment and has previously declined to answer questions about the ongoing investigation.

Attorney Brett Vottero, a former Hampden County prosecutor who handled murder cases under former DA William Bennet, said in an interview it is not abnormal for homicide prosecutions to proceed without an exact cause of death, particularly when victims are not found for months or years after a killing.

"Every case is different and the ability of a medical examiner to identify the precise mechanism of death is going to depend on the condition of the body," said Vottero . "It's certainly not the first homicide in Hampden County where the body was decomposed significantly."

But other legal experts interviewed by MassLive said the phrasing on the death certificate -- "homicidal violence" -- is unusual. While causes of death can sometimes remain undetermined, a listed cause generally includes a specific mechanism of death, like gunshot, asphyxiation or blunt force trauma, said Northeastern University School of Law Professor Daniel Medwed.

"I'm not intimately familiar with the full range of descriptions of cause of death on Massachusetts death certificates, but my initial reaction is it's remarkably vague, nonspecific and unusual," he said. "There would usually be something to describe the behavior, not just 'homicidal violence.' "

Both Vottero and Springfield-based defense attorney John Thompson noted that medical examiners are not limited to purely medical analysis when determining whether a death is a homicide. Forensic pathologists can look at circumstantial evidence, witness statements and police reports when ruling on a death.

And in Weldon's case, such information was abundant -- including allegations of abductions and assaults from living victims and nearly 200 pieces of evidence gleaned from a police search of 1333 Page Boulevard.

"Usually it would say something like undetermined or cannot be determined," said David Siegel, a professor at New England School of Law. "Whenever a body is badly decomposed it makes determining a cause of death more challenging."

It is certainly possible to successfully prosecute a murder without those details, but their absence opens a potential line of argument for Weldon's defense attorney, Siegel said.

"It might raise the cause of death as an issue. I don't think it's a basis to invalidate the autopsy or anything like that, but it might be something to pursue in the defense," Siegel said. "The government has to prove that the defendant caused somebody's death, and that might be an issue."

Thompson said that death certificates, while admissible as evidence in Massachusetts courts, do not typically play major roles in homicide prosecutions. A full autopsy report can have more impact and may include details about injuries that could help prove the victims died by homicide, even if the medical examiner could not identify a specific fatal wound, Thompson said.

"It can be a difficult question," he said. "Sometimes the autopsy will answer that question."

The Weldon case dates back to May 27, when he allegedly fled police who were attempting to pull over his vehicle. The chase ended when Weldon crashed his car into a police cruiser and was arrested.

The arresting officers did not know it then, but they had begun to unravel a homicide case unlike any in Springfield since the 1990s serial killings of Alfred Gaynor. A woman emerged from the car and told officers a harrowing story of sexual assault, saying Weldon, the father of her children, had held her captive, raped her and beaten her with a hammer inside the house at 1333 Page Boulevard.

Days later, Weldon's mother -- the owner of the home -- called 911 and reported a foul odor in her basement. Officers responded and began what would become a days-long search, leading to the discovery of three bodies: one in the basement, one in the garage and one buried under a shed.

After the discovery of the bodies, multiple victims came forward to Springfield police with their own stories of being held captive and assaulted by Weldon.

That alleged pattern of activity could help prosecutors prove their case against Weldon, said Medwed, who described the vague cause of death as a "speedbump" that would not likely derail the case.

"There's this concept in evidence law known as the doctrine of chances. It says if something happens a lot, and it's very unusual, it's pretty strong evidence of it being intentional," Medwed said. "That there were all these other women he abducted could show it was not an accident that these women died, because it was his m.o. to kidnap women and cause them harm."

Weldon is being held on $2 million bail and is scheduled for arraignment on Monday.