There's this thread here: http://apocalypse-world.com/forums/index.php?topic=448.0
Basically, it's hard!
I think the question you need to answer is whether "Do the investigators figure out the mystery?" is really at stake. If it is, then you need to make sure play is fun even if the investigators fail. If it's not, then you need to make sure there's something else at stake. Neither of those seem like easy things.
I heard someone talking about an investigative game where each failure meant there was another murder, and therefore more clues, so you'd eventually succeed, but possibly at great cost. That seemed like a reasonably good middle ground.
In terms of concrete moves, for a police procedural I'd focus on specifics of different investigative techniques:
When you dust for prints, you collect samples of any prints in the vicinity, and roll +focused. On a hit, you get to ask questions.
10+, ask 3
7-9, ask 1
On a miss, the Mystery Master can introduce a complication, a red herring, or else you just can't find anything.How many different prints are here?
How old are the prints?
Was this thing touched by someone?
How was this thing held or used?
When you send a sample (DNA, fingerprints, trace, camera footage) to the lab geeks, roll +hard.
On a 10+, hold 3. 7-9, hold 1.
Spend 1 hold to get one of the following (MM's choice):Introduce a new suspect
Introduce a secondary crime scene
Locate a suspect
Identify a murder weapon
Oh! And of course:
Once per session, when you make a terrible pun over a dead body, take +1 forward. YEEAAHHH!