Lawyer and client are under criminal investigation, lawyer claims "L-C privilege." For how long?

Police want to investigate a lawyer and his client, both of whom are suspected.

  1. Ordinarily, each would be interviewed separately, to see if their stories conflict, etc. But lawyer says other guy’s his client, so he must be in room, which would make investigation difficult, for this interview and subsequent ones.

  2. Lawyer interviewed separately. Asked about other guy, continually says “can’t, lawyer-client privilege.” For how long?

And how does it matter if testimony is under oath, say in a deposition or trial? That is, when it comes to that, rules change?
Note: this issue has been brought up recently and specifically relating to Cheryl Mills and Hillary Clinton, and I’ve seen all sorts of comment tinged politically. I’ve never seen it discussed as law, where I hope it stays, in GQ.

I would think this type of question is standard fare in of law school.

You seem to have a misconception about how police interviews work. Either party can refuse to answer police questions for any reason. If the police want to ask someone questions, he can simply refuse to answer them regardless of whether he is anyone’s attorney or not for as long as we wants. The police will run into due process issues with trying to interview a witness who declines to answer questions at some point if they keep trying. It doesn’t really matter if they claim attorney-client privilege or not. This is a pretty big deal that a lot of people get wrong, and the police routinely try to convince people that they are obligated to answer questions. If someone says they want their lawyer, the cops have to stop interviewing them until the lawyer is present, if the police really want to interview the non-lawyer alone they could try to get a judge to rule that the lawyer is no longer allowed on the case, but it’s not likely to help much (the guy can still demand a lawyer, just not that particular one) and probably won’t succeed unless they’ve already got enough evidence that they don’t really need the interview.

Outside of that, attorney-client privilege pretty much completely stops if the person sought help committing a current or future crime or if the lawyer is involved. This is pretty basic law: When Does the Attorney-Client Privilege Not Apply? | Nolo . In actual cases it can be more complicated because it’s not always obvious that the lawyer is involved, and judges are loath to interfere with that part of the legal process, but the fundamental idea is pretty simple. Also police would generally need to get a specific ruling from a judge to do a valid wiretap of their communications or to search the lawyer’s case files, and would have to be really careful looking into any documents from the lawyers office because it could taint other cases (if they look at his files for another client, that client can argue that any investigation into them was started by the look at confidential information, and possibly get evidence thrown out).

It’s not. “Standard fare in law school” involves issues which actually arise in real life. This one doesn’t, except in the context of a lawyer who assists his client in committing a crime rather than counseling him about one afterwards. And as Pantastic says, the attorney/client privilege is waived when the purpose of the representation is to commit an illegal act.

I believe the issue has arisen WRT certain mob lawyers - possibly Gerald Shargel.