Thirty years ago this summer, the Supreme Court pondered a double murder committed in the course of a robbery in Georgia.

On a November day in 1973, Troy Gregg had shot Fred Simmons and Bob Moore and left their bodies in a ditch. Troy Gregg was a petty thief, but those murders, and the fragmented opinion announced on July 2, 1976, in Gregg v Georgia, changed the fundamental nature of American justice. A few months before Gregg’s crime, an earlier Supreme Court majority had shut down death rows nationwide. Now Gregg the murderer and Gregg the case put American government back in the business of killing.

It’s easy to tally the numerical consequences of Gregg v Georgia: At the time I write, 1,026 executions, with 41 percent of African-American or Hispanic inmates; 858 lethal injections, 152 electrocutions, eleven gassings, three hangings, two firing squads; 123 death-row exonerations.

But there’s also another sort of accounting. No decision since Plessy v Ferguson has so tormented–or so politicized–the American judicial system. Roe v Wade, far better known, may have ignited a generation of antiabortion fanatics, but in the courts Roe’s central findings have been affirmed time and time again. Coming to terms with Gregg, on the other hand, continues to turn the justice system inside out, whether the subject is innocence, race, lawyering or even the method of execution itself.

Less than a week before Gregg‘s thirtieth anniversary, for instance, the collegiality of the new Roberts Court was shattered by a case over the death penalty in Kansas. In a 5-4 majority opinion written by Clarence Thomas, the Court ruled constitutional Kansas’s policy making the death penalty the “default sentence” in cases where juries can’t decide between life terms and capital punishment. Dissenter David Souter, citing those 123 exonerations as evidence of the death penalty’s fallibility, called his colleagues’ position “obtuse by any moral or social measure.” Justice Scalia shot back that death penalty opponents could not provide “a single verifiable case” of an innocent inmate put to death.

Scalia probably did not read the June 25 Chicago Tribune before sending his diatribe to the printer. If he had, he would have seen exactly what he said doesn’t exist: meticulous and persuasive documentation that in 1989, Texas executed an innocent parolee, Carlos DeLuna, despite the real killer bragging to friends and family of his crime and prosecutors knowing about him. It’s in fact the fourth case of probable innocence in a dead inmate–a subject so far off the national radar that at this writing not a single national newspaper has reported the Tribune‘s wrong-man revelation.

The Kansas case which inspired Scalia’s and Souter’s sparring rested on just one “technicality” of the complex capital-sentencing system. But technicality–legal and even medical–is Gregg‘s legacy. In Gregg, the Supreme Court majority said capital punishment could be fairly applied provided that the judicial system embrace an elaborate series of procedures–among them separate trial and penalty phases, aggravating and mitigating factors. Gregg proposed that the messy business of killing be moderated by cool bureaucratic courtroom mechanisms.

The states which revived capital punishment in Gregg‘s wake took this mechanistic approach from the courtroom to the execution chamber. Beginning with Oklahoma most states replaced the brutal violence of the gallows or electric chair with the clinical silence of lethal injection: a poisonous cocktail, sometimes administered by machine, which amounts to a what Columbia University anesthesiologist Mark Heath calls a “chemical veil,” freezing the dying inmate’s features into a mask of tranquility, despite what may sometimes be hideous pain.

That “chemical veil” is now itself at the center of the death penalty debate. Earlier this spring, the Supreme Court agreed that enough evidence exists that lethal injection may not mask pain to permit numerous challenges to execution protocols as cruel and unusual punishment. Indeed the same day that Souter and Scalia faced off over innocence, a federal judge in Missouri put all executions in that state on hold because of his belief that lethal injection violates the Eighth Amendment. (In Missouri, the lethal injections are mixed by an unnamed medical doctor–an interesting interpretation of the Hippocratic Oath. The role of medical professionals–doctors and pharmacists–in lethal injection protocols nationwide is yet another hidden scandal of the system.) The point, of course, is not to find a kinder, gentler execution method, but to ask what social political interests are served by sanitizing state-sponsored killing.

And politics, finally, is the subject. The roads leading into Gregg and out from it were paved with politics more than law. It’s common to say that with Gregg, the Supreme Court reversed the 1972 ban on capital punishment in Furman v Georgia, where the fading Warren Court majority found then-current death penalty laws inherently unequal. Largely forgotten today is the fact that Furman had only solidified a de facto moratorium on executions that stretched back far longer. Ever since World War II the number of executions in the United States had been falling annually; by the mid-1960s courts identified so many flaws and so much discrimination on the nation’s death rows that executions ground to a halt. By the time Troy Gregg’s appeal made it to the Supreme Court in 1976, no one had been executed in the United States for a decade.

Gregg resulted from a decade-long campaign by key Republican strategists: Richard Nixon and his White House Counsel William Rehnquist; Ronald Reagan and Edwin Meese in California (it was then-Gov. Reagan, by some accounts, who first stirred the idea of lethal injection in the 1970s, pointing out that horses on his ranch could be humanely put down with a shot). To them, capital punishment was a way of exploiting public fear of disorder, and particularly of winning the historically death-penalty-friendly South to the GOP column. Over the years since, the key argument they presented for capital punishment as policy–deterrence–has been rubbished by study after study, while every year has brought more evidence of the Gregg system’s inherent unfairness and brutality.

Sustaining that system has required some remarkable intellectual compromises–like the Supreme Court’s bizarre 1993 ruling in Herrera v. Texas, asserting that new evidence of innocence is no bar to an execution. The Supremes finally turned their back on Herrera this year, though Scalia still insists that evidence introduced after trial doesn’t belong in courts.

For more than a few Justices, the contradictions of Gregg finally proved too much. Of the original seven-vote Gregg plurality, two Justices–Harry Blackmun and Lewis Powell–came to publicly regret their endorsement of capital punishment, and another–John Paul Stevens–seems on a case-by-case basis to be headed the same way. Sandra Day O’Connor spent her last years on the Court shutting many of the doors Gregg had opened–execution of juveniles and the retarded, for instance–and expressing her grave reservations about capital representation. Justice Anthony Kennedy seems to have inherited her unease.

Thirty years on, the legacy of Gregg is a killing machine which puts the United States at odds with most of the world, and which sets the US judiciary at odds with the Constitution’s own underlying values. Dissenting in 1976, Justice William Brennan predicted precisely this outcome. The cooly bureaucratic killing mechanisms unleashed by Gregg, he wrote, treat “members of the human race as nonhumans, as objects to be toyed with and discarded.” Brennan understood the continuum between the logic of Gregg and the worst mass crimes of the twentieth century.

It is for this reason, he wrote, that Gregg so undermines the Constitution’s explicit, democratic promise that “even the vilest criminal remains a human being possessed of common human dignity.” If you write a class of people out of the human race, anything is possible.