PHILADELPHIA – An abortion doctor was convicted Monday of first-degree murder and could face execution in the deaths of three babies who were delivered alive and then killed with scissors at his “house of horrors” clinic.

In a case that became a flashpoint in the nation’s abortion debate, Dr. Kermit Gosnell, 72, was also found guilty of involuntary manslaughter in the overdose death of an abortion patient. He was cleared in the death of a fourth baby, who prosecutors say let out a whimper before the doctor cut the spinal cord.

Gosnell, who portrayed himself as an advocate for poor and desperate women, appeared hopeful before the verdict was read and calm afterward.

The jury, which reached its verdict on its 10th day of deliberations, will return May 21 to hear evidence on whether Gosnell should get the death penalty.

Gosnell’s attorney, Jack McMahon, called it a “very difficult case” to defend and said “there’s a little bit of feeling on the defense part of what salmon must feel swimming upstream.”

“There’s a lot of emotion. You have the baby factor, which is a big problem. The media has been overwhelmingly against him,” he said. But noting that Gosnell was cleared on some of the charges, McMahon said the jurors “obviously took their job seriously.”

Former clinic employees testified that Gosnell routinely performed illegal abortions past Pennsylvania’s 24-week limit, that he delivered babies who were still moving, whimpering or breathing, and that he and his assistants dispatched the newborns by “snipping” their spines, as he referred to it.

“Are you human?” prosecutor Ed Cameron snarled during closing arguments. “To med these women up and stick knives in the backs of babies?”

The details came out more than two years ago during an investigation of prescription drug trafficking at Gosnell’s clinic in an impoverished section of West Philadelphia. Investigators said the clinic was a foul-smelling “house of horrors.”

Pennsylvania authorities had failed to conduct routine inspections of all the state’s abortion clinics for 15 years by the time Gosnell’s facility was raided. In the scandal’s aftermath, two top state health officials were fired, and Pennsylvania imposed tougher rules for clinics.

Four former clinic employees previously pleaded guilty to murder and four more to other charges. They include Gosnell’s wife, Pearl, a cosmetologist who helped perform abortions.

Both sides in the highly charged abortion debate endorsed the verdict.

Abortion opponents said the case exposed the true nature of abortion in all its disturbing detail.

“This has helped more people realize what abortion is really about,” said David O’Steen, executive director of the National Right to Life Committee. He said he hopes the case results in more states passing bills that prohibit abortion “once the unborn child can feel pain.”

Supporters of legalized abortion called the case a preview of what poor, desperate young women could face if abortion is driven underground with more restrictive laws.

“Kermit Gosnell has been found guilty and will get what he deserves. Now, let’s make sure these women are vindicated by delivering what all women deserve: access to the full range of health services including safe, high-quality and legal abortion care,” said Ilyse G. Hogue, president of NARAL Pro-Choice America.

Midway through the six-week trial, anti-abortion activists accused the mainstream media of ignoring the case because it reflected badly on the abortion rights cause. Major news organizations denied the allegation, though a number promptly sent reporters to cover the trial.

After prosecutors rested their five-week case, Common Pleas Judge Jeffrey Minehart threw out for lack of evidence three of seven murder counts involving aborted fetuses.