Luigi Mangione

has to stand up to scrutiny

But to what scrutiny, precisely? If a judge decides that certain specific problems with the evidence are inadmissible (including police misconduct and chain of custody issues), what other scrutiny could be given to the evidence?

Judges already have a lot of leeway over how they run trials even within the law, and we're talking about a country that has removed even the pretence of rule of law in the past six months (more, if we go back to the Trump v United States ruling last year).