Each week, In Theory takes on a big idea in the news and explores it from a range of perspectives. This week we’re talking about affirmative consent. Need a primer? Catch up here.

Alan M. Dershowitz is the Felix Frankfurter Emeritus Professor at Harvard Law School.

Affirmative consent, the latest policy intended to prevent sexual assault, has roiled college campuses. Those who advocate for affirmative consent legislation say those who want to have sex should be required to discuss and verbally agree to such activity before it happens. Opponents say that such stringent requirements de-romanticize what should be a subtle, interactive process often based on nonverbal cues.

I believe that there are two separate, often overlapping, issues with regard to consent. One involves individual behavior, an area in which affirmative consent could be a helpful standard. The second, however, concerns our legal system – where punishing alleged violations of such stringent rules without due process may tarnish our principles of fairness.

The first question is whether participants in a potential sexual encounter should require verbal consent before they proceed. Let’s call this the primary rule, because it involves the primary decision: to proceed or not to proceed.

On this issue, I come down squarely on the side of requiring affirmative consent. To defend my point, I would invoke a reverse of the old Blackstonian formulation, a bedrock concept in Western law. In 1765, the English judge Sir William Blackstone wrote that “it is better that ten guilty persons escape, than one innocent suffer.” We can slightly alter the concept when speaking of sexual assault and come to the conclusion that it is better that 10 acts of potentially welcome sex be avoided than that even one act of nonconsensual sex occur. Put more simply, we should always err on the side of being absolutely certain that our potential partners have, in fact, consented.

I have always urged my children, my friends and my students to act on that principle. It may well be true that requiring overt verbal consent de-romanticizes the act under some circumstances.  But that is a small price to pay for avoiding any act of nonconsensual sex, which can be catastrophic to the victim.

The second aspect of the consent rule is what I call the “enforcement principle.” It involves how the system — whether it be the legal system or the academic disciplinary system — decides whether a given sexual act did or did not receive consent. Here I would insist on the actual Blackstonian principle being applied. Even though it is better for 10 potentially welcomed sexual acts not to occur than for one non-consented act to take place, it simply doesn’t follow that the same calculus should be applied in the context of enforcement and punishment on a college campus. In that very different context, it is better for 10 individuals who did not obtain consent to go free than for even one individual who did obtain consent to be wrongfully punished. Being wrongfully punished can be catastrophic for a student.

This is where universities are making a dreadful mistake.  Fearful of being sued by the federal government, many schools have made it easier both to report accusations of sexual assault (a good thing) and to find a student guilty based on low standards of proof (a bad thing).  Rather than requiring proof beyond a reasonable doubt – the standard of evidence required to reach a conviction in a normal court system – many schools are willing to deliver a guilty verdict and permit punishment to be imposed based on a mere preponderance of the evidence: a showing that there is no more than a 51 percent likelihood that the assault occurred.

While that lower standard makes convictions easier to reach, it also means that for every 100 students who are disciplined under this standard, as many as 49 of them may well be innocent.  That ratio is unacceptable in any civilized society that cares about the rule of law and the principle of fairness. Requiring the accused to demonstrate that affirmative consent was obtained, which is often difficult to prove, tips the balance even further.

A wrongful conviction for sexual assault may end a student’s opportunity for further education and a meaningful career, and thus we must not tolerate so high a level of potentially false conviction. So we should stick to the Blackstone formula and demand a high level of proof, even if that means that some sexual assailants may go free. That is the price we pay for our commitment to the presumption of innocence, an essential element of the rule of law.

Hopefully , the primary rule — that we should choose against having sex where consent if uncertain — will reduce the need for applying the enforcement rule — that we should choose against punishing those accused of violating the primary rule where there is reasonable doubt.

Yes, this is complicated. Yes, it means that there is one rule for those who are considering engaging in sexual encounters and another very different rule for those administering punishment.  But sexual assault is a very complicated problem itself, particularly when it comes to the requirement of consent.

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