The Washington Post reports:
Sen. Carl Levin (D-Mich.), the chairman of the Armed Services Committee, suggested that the FBI had done "one heck of a job" so far, emphasizing the need to move Shahzad through the U.S. court system to secure a guilty verdict. "Since he's arrested here in the United States, he's an American citizen, he's going to be entitled to the same rights that other American citizens have. So, you want to make sure you can try and convict this guy, and if you don't do it right, you can mess up your own trial and conviction. So you've got to do it right. Otherwise you're working against yourself, whatever the rights are, including the Miranda warning," Levin said.
John McCain said earlier today on Sean Hannity's radio show that the top priority should be preventing future attacks, not securing a conviction: "When we detain terrorism suspects our top priority should be finding out what intelligence they have that could prevent future attacks and save American lives."
McCain told Hannity that as an American citizen Shahzad "has a right not to self-incriminate." He clarified to Politico that his objection to reading Shahzad Miranda rights is that it shouldn't be done immediately: "What I was talking about was that we don’t have to Mirandize someone immediately. You don’t – before you charge them, there’s time that elapses."
Time reported that Shahzad "was interviewed by the FBI under the Public Safety Exception rule before being read his rights," but it's not clear how long he was questioned before a Miranda warning was read to him.