It was called the Mother's Day Massacre—the brainchild of Harvey Karman, an eccentric California man without medical training who had served 2½ years in prison for performing illegal abortions in the 1950s. Karman teamed with a young Philadelphia doctor who offered to perform abortions on 15 impoverished women, each between four and six months pregnant, who were bused to the Philadelphia clinic from Chicago on Mother's Day 1972.

What the women didn't know was that they were guinea pigs for a device Karman had invented, which he called the "super coil." He had tested it only on wartime rape victims in Bangladesh, where he had traveled under the sponsorship of the International Planned Parenthood Federation.

Complication rates were high, and little wonder. A colleague of Karman's Philadelphia collaborator described the contraption as "basically plastic razors that were formed into a ball. . . . They were coated into a gel, so that they would remain closed. These would be inserted into the woman's uterus. And after several hours of body temperature, . . . the gel would melt and these . . . things would spring open, supposedly cutting up the fetus."

As in Bangladesh, the Philadelphia experiment was a failure. Nine of the 15 women suffered serious complications. One needed a hysterectomy.

The following year, the Supreme Court decided Roe v. Wade. It would be 37 more years before the Philadelphia doctor who carried out the Mother's Day Massacre would go out of business. His name was Kermit Gosnell.

The advent of "safe, legal abortion" didn't interfere with Gosnell's back-alley career. The grand jury's account suggests that other abortionists treated him less as an outlaw than as a niche player in the abortion market. He earned a bad reputation in Philadelphia but received referrals from across the Eastern Seaboard. Many of the women dispatched to him were "well beyond" 24 weeks pregnant, the legal limit in Pennsylvania.

"Gosnell was known as a doctor who would perform abortions at any stage, without regard for legal limits," the grand jury reported. "His patients came from several states, including Delaware, Maryland, Virginia, and North Carolina, as well as from Pennsylvania cities outside the Philadelphia area, such as Allentown. He also had many late-term Philadelphia patients because most other local clinics would not perform procedures past 20 weeks." The woman Gosnell is accused of murdering with a drug overdose, 41-year-old Karnamaya Mongar, came from Virginia and was referred by a clinic either there or in the District of Columbia.

The grand jury did not name any of the clinics, hospitals or doctors who made referrals to Gosnell, except for a Delaware clinic where he also worked part-time. Its narrative suggests, however, that "legitimate" abortionists routinely availed themselves of Gosnell's services to help their patients evade legal and ethical limits on late-term abortion. This may be a fruitful subject for legislative investigation, either in Harrisburg or Washington.

According to the grand jury, Gosnell's method of "abortion" in these late-term cases was infanticide, plain and simple. He or an untrained staffer would induce labor, deliver the baby alive, and then perform the procedure they called by the chilling euphemism "snipping"—slashing the infant to death with scissors to the neck and spine. "Over the years, there were hundreds of 'snippings,' " the grand jury found. But bodies had been disposed of and files destroyed, so the evidence was sufficient to prosecute in only seven cases. One of those victims, a neonatologist testified, was a boy of "32 weeks, if not more, in gestational age." That is, his mother had been at least 7½ months pregnant.

Why were these horrors allowed to persist for decades? Even if the infanticides had been concealed, there were ample other irregularities in the clinic's operations, including filth, unsanitized instruments, unqualified staff and dangerously inappropriate use of drugs. When the clinic was finally raided in 2010, it was the result of a federal narcotics investigation.

Part of the reason for the regulatory failure was simple bureaucratic indifference or incompetence. Inspectors from the Pennsylvania Department of Health visited several times between 1979 and 1993, noted problems, and didn't bother following up. But after 1993, the inspectors never reappeared until the 2010 raid. The reason was political.

In 1994 Tom Ridge, a pro-abortion Republican, was elected governor, succeeding the antiabortion Democrat Bob Casey. According to the grand jury, Ridge administration officials "concluded that inspections would be 'putting a barrier up to women' seeking abortions. Better to leave clinics to do as they pleased." The new policy did away with all regular inspections of abortion clinics. Mr. Ridge's lassitudinous approach was bipartisan, continued by his successor, Democrat Ed Rendell, who resumed the inspections only after the 2010 raid.

Prosecutors are seeking the death penalty for Gosnell and have already obtained guilty pleas from eight of his former staffers. The grand jury's report should also be seen as an indictment of America's post-Roe abortion industry. Its indifference—at best—to legal limits made possible the deaths of untold numbers of babies, lending credence to the argument that legal abortion is a slippery slope to infanticide.

Meanwhile, the claim that Roe v. Wade made America safe from back-alley abortion stands exposed as a cruel hoax, and a deadly one for women and children alike.