Pell Loses Appeal, page-87

The trouble is that previous convictions and information are not supposed to be taken into account in a trial, although we onlookers find the prior evidence compelling of course. The trial should only consider the evidence directly relevant to the case.

I guess you could have a situation where an innocent person, who was falsely convicted for some reason in a previous case, stands trial for a second similar case and the jury hears that he has a prior conviction. Obviously the jury will be tempted to convict for a second time. And so on.