As preposterous as the idea of homosexual panic may sound today, for much of the twentieth century it was treated as something like common sense. “When a beast attacks, you are justified in killing him,” is the way one defense attorney phrased the principle behind it, in 1940. The press, too, sometimes discussed the idea approvingly. The New York Daily News described a 1944 murder of a gay man as an “honor slaying.” In 1952, homosexual panic was listed as a mental disorder in the first edition of the American Psychiatric Association’s Diagnostic and Statistical Manual, and, as late as the nineteen-nineties, the notion was still so current in the popular mind that a Christopher Street shop selling gay-themed T-shirts was called, in what seems to have been ironic homage, Don’t Panic.

It turns out that the psychological concept has a less than illustrious origin. The term “homosexual panic,” Polchin reports, was coined by a psychiatrist named Edward Kempf, in a 1920 treatise titled “Psychopathology.” Polchin garbles a key quote from Kempf, printing “sexually attracted” where Kempf wrote “sexually attractive,” and I took a look at the relevant chapter to see if I could make sense of it. It’s understandable that Polchin got confused. Kempf’s text is neither lucid nor coherent.

Kempf theorized that homosexual panic emerged from “the pressure of uncontrollable perverse sexual cravings,” that is, from the frustration of homosexual urges that typically arose in same-sex environments, such as prison or the military. According to Kempf, symptoms of the panic included a fearfulness that could lead to catatonia, a “compulsion to seek or submit to assault,” and delusional perceptions of being poisoned or entranced. Indeed, the hallucinations and paranoid delusions that many of Kempf’s patients suffered from were quite serious. One patient imagined that broken pills were being surreptitiously put into his pudding; another went through spells of believing he was God.

What was wrong with the patients sounds much graver than suppressed homosexual urges, which, a century after Kempf, no longer seem as monstrous as they may have in his day. Polchin wonders if the men, many of whom were veterans of the First World War, were in shell shock—though an exact diagnosis now hardly matters. The puzzle for a historian to solve is why Kempf strained so hard to pin the misery of his patients on homosexuality. Some of the men in his care did have thoughts about homosexuality, and a few acted on their thoughts, but Kempf interpreted the panic of a man who ate metal polish as “clearly terror at his own homosexual eroticism,” and, when a patient simulated death by lying still on the floor, Kempf observed that “this usually means an offer of sexual submission.” He comes across as a doctor too focussed on his hobby horse to be able to see his patients.

Perhaps Kempf saw every cigar as much more than a cigar because he was under the spell of Freud. In 1911, Freud speculated that delusions of persecution were caused by an unconscious attempt to fend off the idea “I love him” by rewriting it as “He hates me.” The argument was so ingenious that it held sway in psychoanalytic thought for decades. Since Stonewall, however, it hasn’t worn well. Assessing the supposed link between paranoia and homosexuality in a monograph in 1988, the psychiatrist Richard C. Friedman dismissed the notion that “homosexuals are paranoid” as “of course false,” and also denied the corollary, writing, “Not all decompensating, dangerous paranoid patients have homosexual ideation.” Friedman acknowledged that mental illness, fear of homosexuality, and violence could intersect. He recalled that, while serving as a medical officer in the Army, he once examined a paranoid schizophrenic patient who, when Friedman offered him a seat, snarled, “So you think I’m queer,” and attacked; the patient had to be restrained by four men. But Friedman preferred to describe the motive for this kind of rage as “pseudohomosexual”—stemming from a conflicted wish for dependence on a powerful man, rather than from a conflicted wish to have sex with another man. Men who act out such rages, Friedman noted, are not always delusional, and they may direct their rage at women as well as at gay men. The opportunism with respect to targets seems telling.

It took a long time to demote homosexual panic from common sense to history. Polchin organizes his account roughly in chronological order, and from time to time, along the way, suggests that the pattern of the crimes, or at least the slant of the reporting on them, altered with the decades. He notes, for example, that ideas about homosexuality were in such flux in 1919 that, when the U.S. Navy tried to root it out of Newport, Rhode Island, where the Naval War College was in louche proximity to summer homes of the rich and famous, the Navy instructed its undercover investigators to “use your own judgment whether or not a full act is completed.” Somehow the Navy investigators were to think of themselves as set apart from the gay men with whom they were having sex. Polchin sees in the crimes and reporting of the nineteen-fifties, meanwhile, a tendency for heterosexual men to assert masculinity through “violent rejections of queerness,” and a tendency for journalists to drum up panics about geographic clusters of homosexuals. Homosexuals drew crime to a neighborhood because they were the natural prey of hoodlums, the journalists warned. Polchin’s historicizing observations seem valid and accurate, as far as they go, but, if a nineteen-thirties murder was a little more likely to start with hitchhiking, and a nineteen-sixties murder with a pickup in a bar, the variations seem minor compared with the transhistorical—almost ahistorical—sameness of the underlying pattern, a threat that seems to have been a constant presence in gay lives for most of the century.

A seed of change, however, was finally planted in the late nineteen-fifties, when the gay community began to write about such crimes themselves, making visible the complicity of the judicial system and the press in entrenching homophobia. In 1959, for example, the early gay-rights monthly ONE discussed a case in New Orleans in which three Tulane students murdered a man who, they claimed, had made an “improper advance” as they were trying to rob him. After a jury acquitted the killers, the courtroom broke into applause, and a local newspaper ran a photo of the defendants hugging their mothers. The writer for ONE reframed the acquittals as a further injustice: “How many more times must the innocent die and the guilty go free before the unsubstantiated claim of an ‘indecent proposal’ ceases to be an alibi for robbery and murder?” Through such reinterpretations, a new understanding of the crimes became part of the project of gay liberation. In 1984, an executive vice-president of the National Organization of Women pointed out how absurd it was that anti-gay rage had long been considered natural. “I am a lesbian and I have been approached by men in straight bars,” she said. “In discouraging their advances, I have never found it necessary to try to kill them.”

In 1992, the journal Law & Sexuality published a definitive takedown of the homosexual-panic defense, by the historian Gary David Comstock. The psychological literature on the condition was scanty, Comstock noted, and the condition itself seemed largely irrelevant to the murder cases that it had been applied to. Summarizing the work of psychologists who had followed in Kempf’s footsteps, Comstock wrote that the symptoms typical of a man struggling with homosexual desires were “introspective brooding, self-punishment, withdrawal, and helplessness,” which hardly seemed like traits that would give rise to an uncontrollable impulse to kill. And it was far from clear what pertinence they had to the case of a hoodlum who had gone looking for a homosexual to shake down and then lashed out. “Legal defenses have misappropriated the disorder,” Comstock concluded.