acts in the united states. >> pete, how thick is the case law on this not using the miranda warning, how many instances of this do we have that have gone through the system? >> well, it has gone all the way to the supreme court, so there's no doubt that the public safety exception exists, the government has used it before. they exercise it at the beginning and again with ab due ma tal he have. you can understand it. in a terrorism case, it makes sense. you're trying to find out are there other plots, co-c co-conspirato co-conspirators, there's public safety consideration and the courts recognize it. so it is pretty hearty. it would i think stand up if challenged in court. >> nbc news' pete williams. thank you for joining us and thank you for your steady guidance through this week. >> very kind of you.