Edit: The issue of a sleeping judge was raised again in the appeal of Kearns v R  NSWCCA 103. Here the trial judge strongly refuted the allegations against him, and the appeal was dismissed.
I remember hearing a Law Report podcast about a NSW Court of Appeal decision that no miscarriage of justice occurred when a trial judge fell asleep during parts of the trial.
It turned out the judge suffered from sleep apnoea. (If you know someone with it, or are unlucky to suffer from it yourself, you’ll know just how debilitating it can be.)
The Court of Appeal’s decision seemed a little counter-intuitive, and evidently the High Court thought so too.
In Cesan v The Queen (2008) 250 ALR 192;  HCA 52 the High Court held the judge’s sleep caused a miscarriage of justice. That was because the judge wasn’t able to properly supervise the jury and ensure it paid attention to all of the evidence, and wasn’t distracted.
Surprisingly, French CJ cited at  and  numerous authorities dealing with sleeping judicial officers. It seems other appellate courts have also been confronted with this issue.
The typical summary-court workload leaves little time or opportunity for judicial officers to nod off, though I imagine it must be difficult to maintain their attention for all of the time in longer hearings.
Interestingly, the High Court didn’t make any mention of the failure of the advocates in the trial to mention anything to the judge. No doubt they would have felt very uneasy at the prospect of bringing it up — in effect, rebuking the judge. Maybe the judge didn’t realise the effect his medical condition was having on the trial. And maybe, the outcome might have been different if the advocates had mentioned something.
The Law Report transcript has some valid observations on that exact point, and is worth a read.