Real Gang Members Feature as Voice Actors in GTA V - IGN

Turns out that Rockstar used real gang members to use as their voice actors for GTA V, feeling that getting someone who was trained to act like a hardened criminal/gang member wouldn't feel authentic enough.

“When we record all these ambient characters that are in the world we go towards authenticity,”
They look at the lines and they say, ‘I wouldn’t say that. If I was upset at another gang, I wouldn't say that.’ So, well, then say what you would say. Authenticity, you know?
“There’s a lot of sessions that we would have where we would just throw the script on the floor and be, like, 'This thing we wrote is irrelevant, let’s actually work out something real.'”