It is not unusual for an investigation to continue after indictment. A legit prosecutor might find in- or ex-culpatory evidence and make a decision to drop charges on the latter. I know this is a theoretical point with Nifong involved, but it is not unusual to continue an investigation after an indictment.
Destine continues to cover his tracks. This site had a full profile earlier today. Gone now...
http://profiles.yahoo.com/cappadonna21xxx
Yes, investigations usually always continue a lot or at least a little after arrest, but not as a search for your prima facies case let alone your case-in-chief, LOL! On a big case or a case with "hinky" witnesses, you may continue shoring up evidence up to and even into trial, gathering evidence to refute witness testimony, and so forth.