President Trump’s former personal attorney, Michael Cohen, will be on Capitol Hill for hearings from Tuesday through Thursday this week. America — or at least that most important part of America: people who pay close attention to the intricacies of politics — is on tenterhooks waiting for Wednesday’s public testimony before the House Oversight Committee.

Cohen sits closer to more aspects of Trump’s life than any of the other Trumpworld figures who’ve risen to national prominence over the course of the various investigations into the president. He worked for the Trump Organization; he worked for the campaign; he interacted with the president during the White House transition. And his work was focused, it seems, on shielding the most sensitive parts of Trump’s life.

He has already pleaded guilty to having helped Trump orchestrate 2016 payments to two women who alleged affairs with the president, and who knows what other details might emerge? Reporting suggests that Cohen plans to drop new information about Trump’s private behavior and more details about those hush-money payments and a proposed development in Moscow that overlapped with the campaign.

But Cohen isn’t a normal witness able to answer questions at will. He’s bound by three constraints that will likely significantly limit what he’s able to talk about — and what he’s able to learn.

The first limit is the one that’s been most discussed: Cohen won’t go into detail on things that overlap with special counsel Robert S. Mueller III’s probe.

Former assistant U.S. attorney Mimi Rocah, who spoke by phone with The Washington Post, explained that this is likely not just Cohen offering a courtesy to Mueller and his team, who are investigating possible ties between the Trump campaign and Russian government. Mueller’s team and Cohen have a formal cooperation agreement that outlines what is expected of Cohen.

“With a formal agreement like that it would be pretty easy for the special counsel to limit what Cohen says based on what they want him or don’t want him to talk about,” Rocah said. “So it’s not written in the agreement itself, but the agreement binds him to follow whatever conditions they set.”

Given how reserved Mueller has been about revealing elements of his investigation, it’s likely that Cohen is on a short leash. Cohen is not known for a strict adherence to established rules, but if he bucks Mueller, the consequences might be unpleasant.

"Theoretically Mueller could go back and say he breached his cooperation agreement, Rocah said. That could prompt Mueller to return to the court that sentenced Cohen and suggest that his three-year sentence be increased.

Such a request would be somewhat uncommon. “Usually when someone breaches an agreement post-sentencing, you’re more likely to frankly just charge them with another crime,” Rocah said.

There’s another important limit on the week’s testimony: Cohen is still bound by his attorney-client relationship with Trump.

For this, we turn to Peter Margulies, a law professor at Roger Williams School of Law and an expert in legal ethics. Margulies explained that Cohen, as Trump’s attorney, is constrained in two ways. First, Cohen has a duty to maintain confidentiality about his interactions with Trump. Second, he’s bound by attorney-client privilege.

What’s the difference? The latter is narrower, protecting only communications between the two that’s centered on getting legal advice. Privilege is also maintained until waived by the client (here, Trump) or by a court order.

“Cohen can’t volunteer information that is either subject to this duty of confidentiality or is covered by the privilege,” Margulies said. “With respect to all that stuff, he’s obliged to keep his mouth shut, and he can discuss those matters only pursuant to a court order.”

Two asterisks that apply here. The first is one way in which attorney-client privilege can be overridden. There’s a crime-fraud exception, which removes claims of privilege from any communication aimed at furthering or covering up an illegal act. Any issues related to crimes to which Cohen has already admitted — for example, the hush-money payments — Margulies figures that congressional investigators could mandate that Cohen discuss.

The other asterisk is that only communications about legal advice are privileged.

“There’s an open question as to how much of what Cohen did was actually legal in character,” Margulies said. “You can be a fixer and do jobs for someone and happen to be a lawyer, as Cohen was. It doesn’t necessarily mean you’re providing legal advice.”

All of that said, Cohen doesn’t get to simply decide that conversations he had with Trump should be exempt from privilege. Even that discussion of the hush-money payments might not be cleared under crime fraud: Perhaps, Margulies pointed out, Trump could prove that he wasn’t involved in the payments and therefore any conversations weren’t exempted.

Cohen may not even be allowed to answer questions related broadly to his work for Trump. If he were asked how many hush-money agreements existed, that might breach privilege simply because it would reveal information about his conversations with Trump.

If Cohen simply threw caution to the wind and revealed information that is clearly privileged, the ramifications would be limited. Margulies noted that he might be disbarred, but that’s going to happen anyway. Trump could sue, perhaps, but Cohen likely doesn’t have much money to give him. (He might have insurance against such suits, though, Margulies pointed out.)

Setting aside questions of privilege, Cohen may not want to talk about the Trump Organization for another reason: Cohen likely doesn’t want to irritate the U.S. attorney who prosecuted him last year.

Cohen has admitted guilty on nine criminal counts. One was for lying to Congress (as Republicans will certainly note on Wednesday), obtained by Mueller. The other eight were obtained in agreement with the U.S. attorney for the Southern District of New York, commonly referred to as SDNY.

It appears that SDNY is investigating the Trump Organization to some extent. (The company’s chief financial officer has been cooperating with investigators since some point after the investigation into the hush money payments began.) Cohen and SDNY don’t seem to have a formal agreement, Rocah points out, but there is evidence that Cohen is working with them anyway. (A New York Times story this week indicates that he offered federal investigators new information.)

SDNY won’t want Cohen to talk about investigations already underway, given the threat that his comments might pose to those efforts. And Cohen will likely want to respect that wish for a very specific reason.

“My sense is this guy is one way or another looking to reduce his three-year term,” Rocah noted. So he may be “angling for a Rule 35 reduction in sentence post-sentencing.” Under the federal rules of criminal procedure, individuals who have been sentenced for crimes can earn a reduction in that sentence if they “provided substantial assistance in investigating or prosecuting another person” within a year of sentencing.

“If that’s the case then I think he will be likely to stay within the parameters of whatever Southern District tells him, talk about, don’t talk about,” she said. “Because if he’s trying to get something from them, it gives them leverage.”

If Cohen doesn’t care about that, then SDNY’s leverage over him might be minimal.

In sum, though, those three constraints mean that Cohen’s public testimony may offer far fewer bombshells than anticipated. But, again: Cohen has in the past indicated a remarkable lack of concern about doing what he’s supposed to do.