This seems less like a reason to prevent free speech, and more like a reason to sequester juries in advance of a trial, so that they never see the news in the first place. Maybe even have pre-built juries sitting around sequestered and ready to go for whatever case happens to come up. But, you know, that'd cost money.
If it were me, I'd say if the prosecution really has enough evidence to prove beyond a reasonable doubt that the defendant did a crime, an initially positive bias isn't an actual problem. In fact that's how the justice system is supposed to operate (innocent until proven guilty).
