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This account was for entertainment purposes only.
Only Mcnulty lying ass said this once and people ran away with it, but it never was implied at all one, Stringer only gave enough to get him knocked for the rest of his probation, as Stringer and Colvin had map that shyt out already, all them lil nikkas took the gun charges which they aint even stay in for that long.....................................
This is what the wiki page says so I'm going with this:
Barksdale sits at the defense table at a court room with all those apprehended during the bust sitting behind him. The shot has no dialog, so it is unclear just how long Barksdale would be in prison, but it can not be less than five years, and it is implied that he received an additional 25 years for conspiracy to commit murder and weapons charges.
http://en.wikipedia.org/wiki/Avon_Barksdale
Under the circumstances he was caught it isn't hard to see how he could be convicted of conspiracy.