Here's my understanding of what happened: The timeline for this movie was the same as Saw 3. The clip of the autopsy shown at the beginning of the movie actually happens at the end. The bad cop was helping jigsaw in Saw 3 also.
Still a little confused, I have to watch 3 again. I figured it would have to be later because Marky Marks brother was standing on that block of ice thruout the whole movie, then the guy from 3 was there with the chic who had the bullet necklace around her neck which happens at the end of 3... what was donny walberg doing that whole time gap?
I saw it the other night and gathered that it happens at the same time as the 3rd movie and the end where the detective listens to the tape is possibly a precurser to the 5th movie, although the tape wasn't really a challenge.