For my story, the MC is a cop, who becomes obsessed with catching the villains after the villains victimize too many people, including the MC himself. The MC has a suspect, who got off for lack of evidence, and the police do not have enough evidence to get legal authorization to investigate further. The suspect is also laying low after. He knows the police are onto him now, and does not want to make contact with the rest of the gang, which could expose who the rest are, which the police do not know. So obsessed with finding out the truth, and who is behind everything, the MC gets into the suspect's lawyer's records and case file, to find out who hired the lawyer. The MC believes that the suspect was not wealthy enough to afford the team of lawyers, himself, so he gets into the main lawyers records illegally. He does this by either blackmailing an ex computer hacker crook, he knows on parole, or he steals a key card and uses it to illegally enter the law firm and get the file. After finding out who paid the lawyer, a much wealthier and more connected man, the MC believes this to be the villain behind everything most likely. So the MC tails him around on his own time for days. One day, the new suspect he is tailing shoots another character to death, or kills him some other way. The MC cannot stop it in time, but he knows now that should he choose to go after the villain and arrest him, that legally it will be fruit of the poisonous tree, and the MC witnessing the murder, would not be admissible in court. I researched this while writing a story by talking to a lawyer, and he said that a cop cannot a witness to a crime, if he was as a result of breaking the suspect's fourth amendment rights, in the case himself. In this case, the cop, broke into private records to obtain the name of the person, he was following, which is breaking the fourth amendment a cop, and therefore, his testimony cannot be used. So the cop has three choices: 1. He can choose to go after the villain and attempt to arrest him, even though his testimony will not be allowed. He will have to hope that the court can find enough physical evidence that the suspect committed a crime, and rely on the physical evidence alone, without his testimony. 2. He knows that if he arrests the villain it will do no good and get him taken off the case, if the police find out that he violated the villains'fourth amendment rights, so he can say screw it, and let the villain go, and hope that the police find other physical evidence at the crime scene to catch him later. 3. He can attempt to shoot the villain to death himself, and try to make it look like justifiable homicide, since he cannot make an arrest that will stick cause of what he has done. It's kind of like how in the movie Seven: SPOILER The two main cops, broke the suspect's fourth amendment rights, in order to find out his identity and where he lived. They then go knock on his door to talk to him and the villain opens fire on the cops and runs away. The two cops choose to go after him but even if they caught the villain, they would not be able to be witnesses against him in court later, and would have to rely on the physical evidence. In my MC's case what would he do? Would he attempt to shoot back if the villain resisted arrest and ran away, just after shooting a man to death? If so, the MC would have to wipe out him being there at the crime scene. For my story, the MC does not want to be a permanently tainted witness, cause then he will not be able to legally participate in the case for the rest of the story, and will not be able to catch the villain at all, in a way that will stand up in court. So then the story would be over, if the MC were to report what happened. So the MC can either lie, and say he was at the scene for entirely different reasons. But lies are really easy to get caught in and it's going to result in questions after questions, checking out the story several times, etc. Or the MC can erase that he was there physically and not tell the police, but instead plant evidence and frame the suspect. But this means that the MC would have to wipe out the physical evidence, of him shooting at the villain to stop him from getting away. He would have to go find the fired bullets and get rid of them, or at least hope that the police do not check his gun, ever. But of course since the police already know he holds a grudge against the villain, they may ask him to have his gun checked as a formality, if they believe this killer to be of the same group that they know the MC has a grudge against. What do you think? Would he wipe out the physical evidence of him being there, so he can frame the suspect instead? And if so, is that possible to do before any other back up arrives, if anyone heard the shots fired?