In this recent testimony before a London court, Peter Madoff, the younger brother of Bernard Madoff, invoked his Fifth Amendments rights countless times, declining to answer nearly all of the questions asked of him. His testimony raised the question about whether U.S. law can protect a person in an English court.

Those monitoring the case said that because Madoff was physically located in the U.S. and testified via a video link, he was free to exercise his constitutional rights, including the right against self-crimination.

David Cynamon, a partner in Pillsbury’s litigation practice in Washington, D.C., explained that “since he is still in the U.S. and subject to potential prosecution, even if he is testifying in a U.K. courtroom, his testimony could be used in a U.S. action.”

Cynamon added that witnesses in the U.S. must have a “good faith belief” that their answers would subject them to a potential future prosecution.