yassin works with former gang members.ponsible for the knife crime that is going on. cressida dick, the met commissioner, says her officers have built up a database of more than 11100 videos to use as an intelligence tool to help tackle knife and gun crime. detectives say some of the lyrics, the gestures and the hand signals are used to taunt rival gangs, which is why they've asked youtube over the last two years, to take those videos down. this criminologist says artists are trading on the imagery in the videos. people, for some reason, like to tap into that. they tap into the imagery of the violent, young, black felon, drug dealer, gun gang banger, shooting people, stabbing people, robbing people. and unfortunately, these young people know this. and of course, they help to perpetuate. it's like, if you think i'm a dangerous, nasty person, well, you haven't met anything yet. drill is popular. and videos sometimes get millions of hits. but for fans and artists like dj jets, they say violence on the streets was around long