Ronan Kerr murder: Police 'know killers' identities'
Police believe they know the identities of the men who planned the attack on Constable Ronan Kerr and made the bomb that killed him in April 2011.
A senior detective involved in the investigation has told the BBC "significant progress" has been made in the case against the bomb-maker.
BBC NI home affairs correspondent Vincent Kearney reports.
- From the section Northern Ireland