President Trump and special counsel Robert S. Mueller III. (Jabin Botsford; Win McNamee/The Washington Post; Getty Images)

Talks between the president’s criminal lawyers and special counsel Robert S. Mueller III about a possible interview of the president have reportedly broken down as a result of Monday’s raid on the office of President Trump’s personal lawyer, Michael Cohen. This leaves Mueller without the benefit of testimony from the man at the center of his investigation. But outside observers should not fear that this will hinder the Mueller probe.

The reality is that prosecutors frequently don’t get to interview those who may end up as defendants. An interview is voluntary, and in most cases, defense attorneys will see little upside to having their client sit down for a chat with the prosecutors looking to indict. In rare cases, the client may be able to persuade prosecutors to reevaluate their position. But the more likely outcome is that the client ends up providing information that simply helps prosecutors build the case against him. And if the client lies during the interview, he opens himself to additional charges.

In a case such as this, with all of the evidence of potential obstruction that already exists, most criminal-defense lawyers would advise the client not to agree to an interview. That’s particularly true in the president’s case, given the likelihood that he might lie about something and put himself in even greater legal jeopardy. Indeed, his own lawyers have voiced their concerns that Trump might lie as a reason they were reluctant to have him talk to Mueller.

That an interview was being considered at all is probably largely due to politics — the president is not just any client. For most presidents, being seen as refusing to cooperate in a criminal investigation might be political suicide. Past presidents have routinely agreed to be interviewed in criminal investigations involving their own administrations. But as we’ve learned over the past couple of years, many of the conventional political rules don’t seem to apply to this president.

Reports that the parties were close to agreeing on the terms of an interview and were just hammering out the last few details presumably are coming from Trump’s lawyers , and they have the feel of defense “spin” about them: “We were being cooperative, we were so close, but then this crazy rogue prosecutor raids Cohen’s office and upends everything.” The truth is that Trump was never likely to sit for a voluntary interview. It is far more probable the Cohen search simply has given the defense a convenient excuse to refuse to do something it didn’t really want to do.

If Trump refuses to be interviewed, Mueller has the option of subpoenaing him to the grand jury, but he is probably unlikely to do so. The president’s lawyers could mount a legal challenge, and though Mueller would likely win in the end, it could delay his investigation for many months. Once in front of the grand jury, the president could plead the Fifth Amendment and refuse to answer questions — as most lawyers would probably advise him to do — which would mean the delay was for naught. And even if the president did ultimately testify, Mueller has to weigh the odds that he would actually provide truthful information worth the delays and legal battles.

So how could Mueller make his obstruction case, whether in an indictment or — as appears more likely — in a report? The key to obstruction of justice is proving corrupt intent, and Mueller would prove it the same way prosecutors typically do: through circumstantial evidence. This could include the suspicious timing of events; evidence of the president’s actions and their likely consequences; lies and conflicting explanations for the president’s behavior; testimony of those who had conversations with the president, witnessed his behavior, or who were otherwise involved; the president’s own contemporaneous statements about such things as his decision to fire FBI Director James B. Comey; and any notes, emails, or other contemporaneous records that might shed light on the president’s state of mind.

No single piece of evidence makes the case, but prosecutors would string them together until there was no longer any reasonable doubt about the corrupt intent behind the president’s actions.

There is no doubt Mueller would like to interview the president. In addition to the questions about obstruction, prosecutors would love to hear what the president has to say about possible conspiracy with Russians to influence the election, as well as about other allegations swirling around his campaign and administration. But if Mueller thinks he has an argument for obstruction, he doesn’t need an interview with Trump to make that case.