First of all, these types of shows rarely provide the amount of drama needed to sustain a person's attention for the full hour on television, and commercials break it up somewhat. To have a story for a hour and a half nonstop being shown as a movie is not going to work out well. After 20 minutes it started dragging and I ended up skipping ahead, watching a bit and skipping until I got to the end.
There just isn't enough surprises or information in this show to make it this long. It's called editing. The viewer doesn't need to hear about every little story from 20 years ago that brings nothing to the case, and is just filler. This could have been done in 30 minutes or the 45 mins and was perfect for an hour on tv.
Unless there is something extremely satisfying or amazing at the end detective shows like this shouldn't be made this long.