Well , Kate is no detective , so I guess she just obssessed with this method of fingering the culprit and went with it . She probably didn ' t realize how messy it would get from there , though part of me thinks that she wanted to go to jail too for her part in disrupting von Karma ' s investigation in the past . Her codependency to Masters probably played a huge part in it too . As for Simon , most of what was proven wouldn ' t hold up in a court of law , whatever was proven could either a be disproved with some rhetoric and circumstantial evidence or b send Simon away for a couple years and no biggie . Edgeworth loves the truth with a passion and was facing a sociopath mastermind which had caused 3 of his last 4 cases so far . He was too dangerous to be wandering around society . At some point it also became kinda personal for Edgeworth since Simon had messed with pretty much 80 % of the people in the case .