Prosecutors outside Philadelphia recently filed felony charges of aggravated indecent assault against Bill Cosby. The charges stem from a 2004 incident in which the comedian allegedly took Temple University employee Andrea Constand to his home, plied her with drugs, and sexually violated her while she was incapacitated. Constand’s claim mirrors those of dozens of other women who have come forward. The case is shaping up as a classic “he said-she said” case—except for a few evidence matters that could make (or break) the case for the prosecution.

One fascinating issue concerns whether Cosby’s wife Camille will testify at all. A federal judge ruled last week that she must testify at a deposition in a defamation case pending in Massachusetts, which involves various claims by Cosby and seven of his accusers. That’s a civil case, and a deposition at that. Will she be forced to testify against her husband in the Pennsylvania criminal trial?

Jurisdictions normally grant spouses a “privilege” when it comes to testifying against their spouse in a criminal proceeding. That is, a witness-spouse may refuse to testify against a defendant-spouse, even if the prosecution desperately wants this testimony. This privilege is status-based. As long as the spouses are lawfully married, the witness-spouse cannot be obliged to testify about anything: observations, confidences, or events during or even before the marriage. The chief rationale is marital harmony. Given the high stakes in a criminal case, compelling one spouse to testify against another could jeopardize the union.

But Pennsylvania has a somewhat unusual exception to this broad rule of protection: “there shall be no privilege . . . in any criminal proceeding in which one of the charges pending against the defendant includes murder, involuntary deviate sexual intercourse or rape.” The charges against Cosby involve aggravated indecent assault, a second-degree felony, not one of the three more serious felonies listed in the exception. So, it looks as if Cosby would win in arguing his case does not fall within the plain language of the exception. Could the judge rule based on the spirit, if not the letter, of the law that the exception should include other cases of egregious sexual misconduct? I doubt it.

Even if Camille Cosby were somehow compelled to testify through an expansive (and arguably flawed) interpretation of the exception to the Pennsylvania spousal privilege, prosecutors would be limited in what they could ask her because of another privilege. This one is content-based, and safeguards confidential communications that took place during the marriage. Even if she were forced to testify, Camille Cosby could decline to answer questions about any private conversations that she had with her husband that remain confidential. The justification is to preserve the marital bond, even strengthen it by incentivizing spouses to share the most intimate, meaningful details of their lives with one another. There are some exceptions to this rule, too, yet it is far from clear they could apply here.

Two other evidence issues deserve scrutiny. As Jeffrey Toobin wrote in the New Yorker, one critical issue relates to whether the Pennsylvania trial judge will allow accusers other than Constand to testify about their interactions with Cosby. Courts typically ban “prior bad act” evidence designed to show character propensity, i.e., that a defendant has done bad things in the past, revealing a bad character trait, and likely acted in conformity with that trait during the incident in question. It’s considered too prejudicial to the defendant. Yet there are routes around this ban. One route is to claim the evidence is not offered to prove character propensity, but to show the defendant had a particular modus operandi during his dealings with women. How the judge resolves this question will influence the prosecution’s strategy at trial—and possibly affect the outcome of the case.

Consider the topic of hearsay as well. Our rule regime favors direct evidence: testimony from witnesses about what they saw, felt, or experienced. Evidence about what you heard someone else say is viewed with skepticism. Hearsay evidence of any sort—a statement made outside of this proceeding that is offered for the truth of what it asserts—is presumed inadmissible because the statement occurred at a different time and place, and without certain courtroom trappings that give us faith in the accuracy of in-court testimony. There are scores of exceptions, though, situations where that evidence is considered inherently trustworthy and/or necessary to a case and therefore admissible.

One of those exceptions comes into play here. Cosby testified at a deposition in a different civil case brought by Constand years ago. A judge unsealed the deposition transcript over the summer, revealing a number of statements by Cosby that could potentially hurt him at trial. Those statements are admissible in the Pennsylvania criminal case; your own past statements, wherever and whenever made, can come in against you at trial if you are a party. Cosby will no doubt contest the admissibility of these statements—perhaps by arguing he was under the impression the deposition could not be used against him at a subsequent proceeding—but I imagine the judge will let them in regardless of whether Cosby testifies. If Cosby does take the stand, the deposition statements can also be used to impeach his testimony by showing inconsistencies between what he said then and is saying now.

Although this discussion is rather technical, let’s not lose sight of the big picture. The resolution of these evidence issues may determine Cosby’s fate. And this case could represent the sole

opportunity to hold him criminally accountable for his purported sexual misbehavior. Under Pennsylvania law, prosecutors must initiate criminal actions for most sex offenses within twelve years of the assault. Prosecutors made it in the nick of time, submitting charges against Cosby just days before the statute of limitations period would have expired. Prosecutors elsewhere might not have this option. The allegations against Cosby go back decades; California, for instance, has a six year statute of limitations for most sexual assaults. There is reason to believe that other potential criminal actions across the country may very well be time-barred.

When it comes down to it, the Pennsylvania criminal matter is just a single case. Cosby, like all criminal defendants, will receive the presumption of innocence and can only be convicted if his guilt is proven beyond a reasonable doubt. He’s faced civil lawsuits before. But now, for the first time, his liberty is on the line. The American public will pay close attention, with the case carrying the symbolic, cumulative weight of years of whispers that have recently transformed into screams.

A professor at Northeastern School of Law, Daniel Medwed is a legal analyst for WGBH News.