It's a good question, so if you have thoughts you might comment over at Volokh, where Adler discusses a new case on that issue -- one where the defense counsel fell asleep during the cross-examination of the defendant.
In every trial I've had that lasted over one week, someone fell asleep at least once, usually in mid-afternoon well into the trial. The strangest occasion was during a bench trial when the judge fell asleep. The opposing lawyer and I made eye contact, wondering what to do. IIRC, the other lawyer made an unusually loud throat clearing noise and the judge perked up.