In 1944, in New York, a decade before Allen Ginsberg, Jack Kerouac, and William S. Burroughs would publish their countercultural works, there was a killer in their midst. Lucien Carr was a brilliant Columbia University student from a prominent Midwestern family. He had introduced the three men to one another and was at the center of the circle of friends that defined what was later known as the Beat Generation. The nineteen-year-old Carr stabbed another member of the group, David Kammerer, in Riverside Park, with a Boy Scout knife, and dumped his body in the Hudson River. Carr claimed that Kammerer, his former scoutmaster, who was thirty-three, had followed him for years, from city to city, and made “indecent” advances. The New York press, defending Carr, portrayed the killing as an “honor slaying.” Although he was charged with murder, prosecutors allowed Carr to plead guilty to the lesser crime of manslaughter. He served two years in a reformatory and then lived out his life as a respected news-agency editor.

Lucien Carr. Photograph by Barney Stein / New York Post Archives / Getty

The case was one of the first high-profile instances of a “gay panic” defense, in which a person claims that his violent act was a sudden emotional response to an unwanted advance from a person of the same sex. If believed, a defendant’s crime may be reduced, from murder to manslaughter, or from attempted murder to assault. A defendant might even raise it as a full-fledged defense to try to avoid liability altogether, but judges and juries have been much less amenable to it in recent years. Since the nineteen-sixties, the gay-panic defense has been used in half the states, but in relatively few reported cases, numbering in the dozens.

The case that brought the defense renewed attention was the killing, in 1998, of Matthew Shepard, a gay student at the University of Wyoming, who was robbed, beaten, and set on fire by two men. At one of the defendants’ murder trials, the defense provided evidence—later admitted to be false—that Shepard had been sexually aggressive. The defendant claimed that his own childhood history of being sexually bullied by another boy caused him to lose control of himself after Shepard’s alleged unwanted advance. (Later reporting suggested that the accused had had a prior sexual relationship with Shepard.) The jury ultimately convicted the defendant of felony murder, which was less serious than the first-degree-murder conviction sought by the prosecution, but more serious than manslaughter, which had been sought by the defense. He was sentenced to two life sentences in prison.

In June, the New York State Assembly joined six other state legislatures that have passed bills banning gay-panic and trans-panic defenses. The New York bill provides that a “non-violent sexual advance” or “the discovery of a person’s sexual orientation or gender identity” cannot serve as the “reasonable explanation or excuse” needed to reduce charges from murder to manslaughter. (Another half-dozen states have introduced similar bills.) Also in June, Senator Edward Markey and Representative Joe Kennedy, both of Massachusetts, introduced federal bills to ban gay- and trans-panic defenses for federal crimes. These moves arise from recognition of the high rates of homicide and other violence perpetrated against L.G.B.T.Q. people, and concern that defenses implicitly blame gay and trans people for violence against them or imply that their lives are worth less than others. What the bills leave in place, however, is a defendant’s ability to claim that his own past trauma can explain the extreme reaction to a victim’s conduct.

The gay-panic defense grows out of the traditional legal doctrine known as “provocation,” which dates to sixteenth-century England and remains in use in American courts. The doctrine allows a defendant to claim that another person’s inflammatory conduct caused a sudden departure from rational judgment, and so an act of killing by that person was done in the “heat of passion.” The traditional paradigm for the defense was a man killing his wife’s paramour upon unexpectedly discovering them in flagrante delicto—a reaction that was then considered reasonable. In addition to a spouse’s adultery, classic provocations included combat, a serious assault, an illegal arrest, or the injury or abuse of a close relative. For centuries, courts limited provocation to these specific categories and inquired whether the situation was sufficiently provoking to cause a blood-boiling homicidal response in a reasonable person. But its use inevitably implied that the victim-provocateur was at least partially to blame. The notion of a “true man” lashing out at another male who purportedly offended his masculinity with sexual overtures fit the male honor norms that informed criminal regulation of violence in the nineteenth century. But the homosexual-panic defense did not formally appear in legal opinions until the nineteen-sixties.

In the middle of the twentieth century, progressive criminal-law thinkers called for the expansion of the provocation concept to accommodate defendants whose situations didn’t fit the narrow categories that courts had developed. Their intent was to make the criminal code more forgiving of human fallibility. Following the standard proposed by the American Law Institute’s influential Model Penal Code of 1962, New York liberalized its provocation doctrine, in 1967, to allow reduction of murder charges to manslaughter when a defendant killed while “under the influence of extreme mental or emotional disturbance for which there is reasonable explanation or excuse.” This shifted the focus toward a defendant’s troubled internal emotional state, rather than demanding that the external circumstances display certain established types of facts. By 1976, New York’s highest court noted that advances in psychology had made the public willing to reduce responsibility for “those whose capacity has been diminished by mental trauma.” What could explain a defendant’s “extreme emotional disturbance” and excuse the violence was a trauma that developed “for a substantial period of time, simmering in the unknowing subconscious and then inexplicably coming to the fore.” If a defendant’s trauma was the key to his defense, his own past was prologue.

Current efforts to ban gay- and trans-panic defenses are uncontroversial in jurisdictions that embrace gay and transgender rights. But doing so may have unintended legal implications. Women who have killed abusive men have sometimes claimed that their charges should be reduced, even when they were not fighting off imminent death or serious injury, which would be valid self-defense. For decades, courts have allowed battered women to argue that their homicidal response was reasonably induced by a male victim’s past abusive conduct. In fact, according to the legal scholar Aya Gruber, women have been more successful than men in using the provocation defense. This is likely because female defendants have more readily proved that they suffered prior trauma. That raises the question of what should be the range of a woman’s reasonable response to a man’s unwelcome sexual advances. If she panics and kills in a social context that makes women’s fear of male sexual violence widespread and ordinary, should her response be considered reasonable and her responsibility mitigated?

The new bills bar both women and men from making a “gender panic” defense. They refuse to excuse, for example, a woman who kills a person who is sexually aggressive but not violent. But they would allow a woman to claim that a reasonable explanation for her homicidal reaction to a nonviolent sexual advance was the trauma caused by a past sexual assault. That defense would be possible regardless of the deceased person’s sexual orientation or gender identity.