John Doe's plan and Mills-spoiler

Ok so the plan did not have to involve a cop with a wife. He would find a cop and find something he liked and take it from him, creating ENVY and WRATH? Makes a lot more sense then. The only thing that still kinda bugs me about it he planned so well and in advance. They found that one guy exactly one year after he started torturing him to the day. If it was so well planned, seems like he would have also planned who his victim was going to be. But he couldn't have known who would be assigned the case, so maybe he planned on just finding who it was and then finding their weakness. After all the planning, that's one wildcard he would have had to deal with that could have messed up his plan. But your explaination makes more sense than anything else I have thought of and helps tie it together. Thank you for the input. I was assuming he needed a cop with a wife, and that's where I was thinking wrong.