According to this account at Lawfare, he's recevied his Miranda warning while in the hospital and federal public defenders (Miriam Conrad and William Fick) have been provisionally appointed to represent him. The transcript of the bedside proceedings, conducted by a US Magistrate Judge, is here.
One of the traditional norms for our lawyers is, "Never to reject, for any consideration personal to himself or herself, the cause of the defenseless . . . ." As was the case when the so-called American Taliban, John Walker Lindh, was defended by some of our country's best lawyers, it's a strength of our system that very talented lawyers are now looking out for Tsarnaev. In the recent past we've seen lawyers step forward for Anders Breivik (in Norway), Ted Kaczynski, and other notorious accuseds.
[edited] I'm working my way through the transcript. It's odd how ordinary most of the words were, given how extraordinary the situation and setting were. But as familiar as the transcript might seem in places, you don't often see them start this way:
THE COURT: I will ask the doctor whether or not the patient is alert. You can rouse him.
DOCTOR ODOM: How are you feeling? Are you able to answer some questions?
THE DEFENDANT: (The Defendant nods affirmatively.)
A few seconds later, the defendant was informed that he could face the death penalty.