What of substantial assistance?

Professor Frank Bowman and this morning’s great Wall Street Journal article (available here with subscription) get extra points for flagging the way a change to advisory guidelines could impact the operation of 5K1.1 and the authority prosecutors used to have to be the sole determinator of whether defendants could receive a mitigated sentence based on cooperating in the investigation and prosecution of others:

[Professor Bowman] pointed out that in many cases, prosecutors persuade defendants to plead guilty and cooperate by promising to reward them for “substantial assistance.” Under the guidelines, defendants who receive such recognition are exempt from the guidelines’ strict provisions. Now that the guidelines are only advisory, defendants may see less need to cooperate. “The Department of Justice has just lost all of its bargaining leverage” with defendants, asserts Prof. Bowman.

I would be especially eager to see comments from prosecutors and defense attorneys about how Booker changes the dynamics around cooperation.