Tens of thousands of Russian criminals – murderers, rapists, robbers – were recruited from prisons by the mercenary group, Wagner, to fight in Ukraine. Now, after six months on the battlefield, the survivors have returned home, with official pardons. Many served only a fraction of their original sentences. And now, they're officially treated as heroes - protected by a new law which criminalises discreditation of anyone who fights on the Russian side in the war.

Already, some returnees are reported to have committed further serious crimes. One has confessed to the brutal axe-murder of his 85-year-old former landlady. In another case, an ex-convict believed to have served with Wagner has been charged with masterminding the killing of two children's entertainers, one of them a 19-year-old woman who was training to be a teacher. The murders in southern Russia provoked an outpouring of anger and grief, with thousands signing a petition demanding that the alleged ringleader - who denies any guilt - should get a life sentence if he is eventually convicted. But they know any punishment will probably be less severe, because the criminal records of former Wagner mercenaries have been wiped. They start their lives again from a clean slate, and if they re-offend, no previous convictions can be considered.

Reporter Arseny Sokolov talks to the mother of the murdered entertainer, to campaigners for prison reform - and to an ex-convict who fought for Wagner - to investigate what threat the returned mercenaries pose in their home towns and villages - and to assess the damage "legal nihilism" is doing to Russian society.

Producer: Tim Whewell