The son of the late notorious John Gotti Sr. Junior gets racketeeting charges droped after the prosectuion fails to convince the jury that Junior is guilty. Four failed trials and he is a free man. The main question that comes to my mind is the idea from old mobseter movies, when the mob always manages to get to some of the jury members and threatens their families lives if they don't go their way. Now the fact that they tried to prosecute him with four different juries and failed only goes further to support my assumption.
http://www.cnn.com/2010/CRIME/01/13/new.york.feds.gotti/index.html?iref=allsearch
If you really are interested in your theory on how the mob gets ahold of some of the jurors in their trials, you should check out the movie "The Juror." It's a great movie with some well known actors & actresses, such as Demi Moore & Alec Baldwin.