Board Thread:Introductions/@comment-2188103-20170813171926/@comment-1894786-20170815011253

Spider-Man testified against JJJ in court in She-Hulk's title, but had to drop the case when Peter Parker would've had to pay millions to Spider-Man as a settlement lol

Also, a ton of supers testified for Hector Ayala's trial in Daredevil.

So there's definitely precedent of heroes in costume testifying in court.