I haven't really delved into this case, so perhaps the argument is just over sentencing. But if the judge were incapacitated throughout the proceedings, the whole conduct of the trial could be questioned including rulings in admissibility of evidence, rulings on attorney objections, etc.
As with most serious cases, I expect there will be appeal after appeal and, in the long run, it seems to me most efficient to throw the original trial out and start fresh so that the starting point for any appeal is a fair trial conducted by a competent judge. But that's just my opinion ...