. >> ken coghlan: it's virtually impossible. >> stahl: ken coghlan is a defense attorney in oxford whoas represented many ole miss students who became confidential informants. he says that, because there are no standardized rules, cops can ask for any number of buys, like metro's ten, which he says is so high, it creates a perverse incentive for kids to entice other kids to break the law. he told us he has seen it again and again. >> coghlan: they don't know ten drug dealers. and they're so desperate, they will go to their friend or their roommate or their frat brother, and they know this person smokes marijuana. and they'll say, "i'm out of weed. can i get ten dollars' worth of weed from you?" >> stahl: your personal stuff. >> coghlan: that's entrapment, and that's not allowed under the law. >> stahl: entrapment, because that frat brother with his own marijuana, was only guilty of possession, a misdemeanor under mississippi law. but if he says yes and sells a little to his buddy, he's now become a dealer-- a felon, facing possible prison time. >> coghlan: and at that point, we're not