"Genocide isn't a crime that grows old." A man accused by Rwandan authorities of participating in one of the worst atrocities of the 20th century is living in Australia's suburbs, a joint Four Corners and Guardian Australia investigation has found. More than half a million people were killed during Rwanda's genocide against its Tutsi minority in 1994. Thirty years on, Guardian reporter Ben Doherty travels to Rwanda to investigate the allegations - and confronts the man accused of being involved in several killings, who is now an Australian citizen. The findings of the year-long joint Four Corners and Guardian investigation raise tough questions about Australia's immigration screening processes.