PHILADELPHIA - The high-profile murder trial of a Philadelphia abortion provider sparked courtroom debate Monday over when life ends, a tweak of the politically charged question of when life begins.

Dr. Kermit Gosnell, 72, faces capital murder charges in the deaths of four aborted babies, described by prosecutors as viable, born alive and then killed at his busy West Philadelphia clinic.

In closing arguments, Assistant District Attorney Ed Cameron called Gosnell's operation an assembly line where a stream of poor, mostly minority women and teens endured hours of painful labor and delivery because Gosnell did not successfully abort babies in utero. He instead killed them with scissors after they were born, authorities said.

"Are you human?" Cameron asked Gosnell, "to med these women up and stick knives in the backs of babies?"

The doctor sat calmly at the defense table, as he has throughout the often graphic six-week trial.

Eight former workers have pleaded guilty to murder or other charges and have testified to seeing babies move, breathe or whine. Yet some said they did not consider the babies fully alive until they were charged after a 2011 grand jury investigation.

Defense lawyer Jack McMahon has seized on that point and argued again Monday that the occasional spasms the workers saw were not the wriggling movements of a newborn baby. And he said prosecutors preyed on workers' emotions and fears to manipulate them into taking pleas that were not always warranted by the facts.

"They should be ashamed of themselves for that," McMahon argued.

He acknowledged that jurors have seen graphic, even grisly, photographs of aborted babies and bloody medical equipment.

"Abortion - as is any surgical procedure - isn't pretty," McMahon said. "It's bloody. It's real. But you have to transcend that."

And he refused to back down from aggressive opening remarks in which he called prosecutors "elitist" and "racist" for pursuing his client, who is black and served mostly poor, minority women.

"We know why he was targeted," McMahon said.

Gosnell is also charged with third-degree murder in the overdose death of 41-year-old Karnamaya Mongar, who came from Virginia for an abortion in 2009.

Among the 54 prosecution witnesses was another Philadelphia abortion provider who said he had performed 40,000 abortions over a 35-year career. He said he only performed abortions up until 22 weeks and did them after 17 weeks at a hospital.

By contrast, Gosnell performed third-term abortions and had two mentally unstable medical assistants and a teenager on duty delivering anesthesia the night Mongar came in, Cameron said.

"If that doesn't tell you right away what kind of practice Dr. Gosnell ran, nothing will," Cameron said.

One assistant warned Gosnell midway through the abortion that Mongar had no pulse, but he nonetheless finished the procedure, witnesses said. It took more than an hour to get her out of the clinic and to a hospital, where the recent refugee, who spoke no English, was pronounced dead the next day.

McMahon argued that prosecutors who blasted the clinic as a "house of horrors" sensationalized the case to make headlines.

"This isn't a perfect place by any stretch of the imagination - but it isn't what they say it is," McMahon argued.

Also on trial is former clinic employee Eileen O'Neill, 56, of Phoenixville. She is charged with theft for allegedly practicing medicine without a license. O'Neill's lawyer said in his closing arguments that prosecutors failed to prove their case against her.