Brock Turner, right, makes his way into the Santa Clara Superior Courthouse in Palo Alto, Calif. (Dan Honda/Associated Press)

KC Johnson is a professor at Brooklyn College and the CUNY Graduate Center. Stuart Taylor Jr. is a nonresident senior fellow at the Brookings Institution.

Last week, a California judge sentenced former Stanford University swimmer Brock Allen Turner to six months in jail for a horrifying sexual assault on an unconscious, alcohol-impaired woman. The resulting uproar over the sentence’s undue leniency risks missing the most important lesson of the case.

Contrary to campus conventional wisdom, the Turner case shows that the best way to deal with a campus sexual assault problem is to rely on law enforcement professionals to protect women and to pursue justice, not on campus disciplinary systems run by amateur sex bureaucrats.

The backlash against Turner’s sentence is being exploited by a powerful but misguided movement to delegitimize law enforcement as the best way to handle campus sexual assaults. The accusers’ rights group Know Your IX has claimed that even reporting an assault to police could harm campus victims. “#copsoffcampus,” the group recently tweeted.

A myth that our universities are mired in an epidemic of sexual violence fuels this movement. Campus activists, the Obama administration and many in the media have used discredited surveys claiming that there are hundreds of thousands of campus sexual assaults annually to degrade due process protections for accused students.

Santa Clara County Superior Court Judge Aaron Persky could be removed from the bench in a recall effort prompted by the six-month sentence he handed down in the Stanford sexual assault case. (Gillian Brockell/The Washington Post)

Still, the 4,959 rape allegations reported by universities in 2014 alone are more than enough to call for the best possible protections. And the handling of the sexual assault by Turner in January 2015, while his victim was lying helpless on the ground outside a campus party, shows how those protections can work.

Two students saw Turner on top of the victim, rushed to her aid and restrained the intoxicated Turner. Police were called and found the now 23-year-old victim “completely unresponsive” and partially clothed. They interviewed the witnesses and secured physical and medical evidence. Prosecutors won a jury conviction of Turner, now 20, for sexual penetration of the victim with his fingers. They asked Santa Clara County Superior Court Judge Aaron Persky for a six-year state prison sentence.

We understand the victim’s pain and outrage at the leniency of the judge’s sentence — six months in a county jail, plus three years probation and lifetime registration as a sex offender. But we also understand how much better the criminal-justice system operated than the alternative likely would have.

Campus activists at Stanford and nationwide have championed secretive disciplinary processes run by administrators who know little about gathering evidence (or about fair procedures). Indeed, had this case been initially channeled through the school, critical evidence — including Turner’s highly incriminating statement to police — might have been lost.

The Obama administration now requires schools to use the lightest possible burden of proving guilt — by a mere preponderance of the evidence — in handling sexual assault cases. The procedural rules are systematically slanted against the accused. And accusers are not subject to meaningful cross-examination, which the Supreme Court has called “the greatest legal engine ever invented for the discovery of truth.”

The result has been the expulsion as sex offenders of many innocent or probably innocent students — in dozens of cases that we have studied — as well as guilty ones. The innocent face lives ruined by terrible injustice. The guilty often go free, expelled from school but walking the streets having faced no criminal penalty at all. Such outcomes do less to make campuses safe than would the robust law enforcement presence that accusers’ rights activists and university leaders oppose and that brought Turner to justice.

Stanford’s disciplinary process for sexual assault accusations prevents the accused and his representative from cross-examining the accuser or any other witnesses. Adjudicators have been trained that an accused student’s acting “persuasive and logical” should be considered a sign of his guilt, and warned to be “very, very cautious in accepting a man’s claim that he has been wrongly accused of abuse or violence.”

For these and other reasons, a campus finding of guilt inspires little public confidence that justice was done.

By contrast, in the Turner case police and prosecutors did what they do best. The defendant was presumed innocent until proven guilty beyond a reasonable doubt. He had a lawyer who could test the credibility of all witnesses, a right to exculpatory evidence, an impartial jury of his peers and other protections against wrongful conviction. The public nature of the trial provided a check against misconduct, either by law enforcement or by the university.

Despite criticisms of the sentence, Persky appears to have presided fairly during the trial. He based his sentence on the recommendation of the probation office, a common approach for judges. While Santa Clara County District Attorney Jeff Rosen sharply disagreed, he has also condemned the recall drive mounted against Persky.

Yes, six months is too short a jail term. But it may also be the least of Turner’s punishments. The stain and notoriety of his crime will mark this champion athlete turned registered sex offender for the rest of his life, everywhere he goes. As it should.