Two medical examiners called by opposite sides in a Fort Worth, Texas, murder case agreed on the cause of death of a man hit by a car and left in the driver's windshield: blood loss.

Where they disagreed was in how much expertise the driver, Chante Mallard, would have needed to save the man's life.

The medical examiner of Tarrant County, who conducted the autopsy on victim Gregory Biggs, charged that the defendant — a certified nurse's assistant — had enough medical training to save Biggs' life.

Dr. Nizam Peerwan, testifying on the third and last day of prosecutors' case against Mallard, said none of the injuries Biggs sustained from the Oct. 26, 2001, impact would have proven fatal had he received prompt medical attention. 

"He certainly would have lived," he testified.

The blood-stained console from Mallard's 1997 Chevy Cavalier

But the medical examiner of Bexar County, paid as an expert witness by the defense, testified that Mallard's occupation was mostly caring for patients, not administering medical care.

"What they do is they change the bed linens, they take away urinals, they dress the patient, wash them," testified Dr. Vincent DiMaio, who is based in San Antonio. "It's more custodial care than true medical care. They may take some vital signs, but it's mostly providing care like a mother caring for a child rather than nursing."

But DiMaio, the defense's only witness, did acknowledge that part of Mallard's training would have involved calling for help, something Mallard failed to do after striking Biggs on her way home from a night of drinking and drug-taking in Arlington, Texas.

She drove eight miles with Biggs still lodged in her 1997 Chevrolet Cavalier and parked the car inside her garage, where he died hours later. Even leaving Biggs on the side of the road would have increased the victim's chances of survival, Peerwan said, since no one could have seen him inside a closed garage.

Biggs suffered broken bones and a nearly severed leg, Peerwan said. He likely lived several hours after the crash, he said, adding that a person can lose as much as 40 percent of his blood before bleeding becomes life threatening.

"He does not have injury patterns that are consistent with instantaneous death," Peerwan said.

Jurors winced as they examined gruesome photos of Biggs' body entered into evidence.

DiMaio confirmed much of Peerwan's testimony, but did say that the way Biggs' body was contorted inside the car could have prevented him from breathing properly, contributing to his death. 

Dr. Vincent DiMaio

"The lack of oxygen made it worse," he said. "It definitely didn't do him any good."

DiMaio also raised questions about whether Biggs was conscious, since he likely would have suffered a concussion from the impact of the windshield.

Under cross-examination, DiMaio testified that, if Biggs had loss consciousness, it would not contradict accounts of him moaning or moving, since it is possible to do so while unconscious. 

Testifying in between the two doctors was Brandon Biggs, the victim's 20-year-old son, who offered little evidence related to the accident but provided a sentimental portrait of his father.

Gregory Biggs may have lived in a homeless shelter, but he wasn't always down-and-out, according to his son.

Brandon Biggs, the victim's son

The 37-year-old former bricklayer lost his truck and his home after suffering from schizophrenia. He fell into further financial hard times after lending money to a former girlfriend.

While living in the shelter, Biggs continued to work a construction job.

Brandon Biggs had filed a wrongful death suit against Mallard, which has since been settled out of court.

Mallard, who at times appeared to be on the verge of dozing off throughout testimony, faces life in prison if convicted of felony murder.

Closing arguments are slated for Thursday morning. The trial is being broadcast live on Court TV.