For my story, the main character, a cop, has a personal grudge, against the leader of a gang but does know he is is. Just a mystery man who got away with his crimes. The MC blackmails a parolee, who was a computer hacker in his criminal days, and gets him to hack into one of the gang members personal information and banking. From there, he follows a money trail, leading up to the leader, and from there, he finds out who the leader is. He starts tailing the leader to see if the leader will give him any leads or angles he can use to build a case. However, while following him the leader commits murder and gets away with it, because the one witness, the MC found him through computer hacking so his testimony as a witness is not admissible in court, so he does not report it, knowing that. The leader also wore gloves when committing the murder, and any DNA found, is not on file, so the only evidence they have is tainted testimony. Now this is where it gets tricky, because the MC needs to come up with a new strategy to get evidence on the leader. Now in most stories, that deal with this scenario, a piece of evidence is tainted, and as a result, the villain walks. It's up to the MC to then get NEW evidence. But in my story's case, it's different because since the leader's identity was discovered through illegal computer hacking, the villain himself is tainted therefore. When the villain is entirely tainted himself, how can the MC untaint him? Because it seems that legally any new evidence, the MC gets will not matter, since the suspect himself is tainted. What do you think? Is their a legal way the MC can get around that? Thank you for any advice. I appreciate it .