'The one piece of evidence' (spoilers)

You don't make a case, especially a murder trial, out of circumstantial evidence. Everything you have cited would be countered by a good defence lawyer on the grounds that she was running away from an abusive husband. In fact the details you cite would help her, rather than harm her.

The recorded 911 call at the end would destroy Mike.

I don't believe it would have been an open and shut case.

1) She gave the boss her real name and past work history and told him she was running away from an abusive husband, so she could use a false name with every one else.

2) She never denied knowing Mike. After all the whole setup was made to look like he was her jealous boyfriend and killed her husband and raped her out of rage since she and her husband were reconciling.

She played him!

I remember having a lot of the same thoughts when I saw this years ago. I believe his story would have certainly given the insurance company pause in paying her - or at least cause to investigate. Thought it was a bit too tidy of an ending- but somewhat forgivable in an otherwise stellar film.

As someone already pointed out, a lot could be covered under the pretense of running away from her abusive husband. Mike's friends at the bar knowing about them doesn't prove or disprove anything.

Plus, two things about the PI:

For one, he didn't see anything because he was repeatedly foiled by her when he tried to follow her. Secondly, Mike didn't know anything about either of the PIs. So the chances of the second one coming to his aid seem slim. The only possible thing that would make her look suspicious is the fact that she made a false report of the second guy exposing himself to a minor. But whether that would be considered relevant to the trial or not, or even come up, I don't know. My guess is wouldn't factor in, because Mike is the defendant and he probably wouldn't have access to any info the police may have about those guys that Clay hired. If that somehow came up, maybe it would be enough to make the jury doubtful, especially in the light of another PI actually being killed when dealing with her.

IMO you have to think long and hard to come up with something to start "discounting" this movie. It was unbelievably entertaining and I don't see how a plothole "spoils" a movie this good if you can't actually spot it while you're watching it.

Also the people at the store where she bought four sets of handcuffs would probably remember her.

I have to laugh at the people who believe she would just get away with it. There is absolutely no one who could vouch for her, the entire town knew what kind of bitch she was. Once Peter Berg came to the realization how she used him all along, any detective would see his story checked out. Too many people would confirm it and the death of the black detective would certainly make her suspicious. The cops would soon discover there was more to her.