>> murad: never. >> pelley: in 2015, just a year after we met her, nadia murad asked the security council >> murad ( translated ): i've seen what they've done to boys and girls. all those who commit the crime of trafficking and genocide need to be brought to justice. >> pelley: the security council voted to approve a first step. in 2017, it created an investigative team to collect evidence of isis's crimes in iraq. the team began exhuming some of the 202 mass graves that are known. now, the question is whether the evidence will ever be heard. iraqi courts are convicting thousands of isis suspects of terrorism, but none has been tried for the crime of genocide against the yazidis. small pockets of isis fighters remain in syria and iraq. but u.s. and iraqi troops have shattered isis as a cohesive military force. is that justice? >> clooney: absolutely not. you know, if you speak to yazidi witnesses, victims, survivors, they will say, "it doesn't help me if somebody's killed in a drone strike." in terms of justice, that means something very different. that means being able to be in a courtro