National Police Commissioner General Fannie Masemola says they are making progress on the assassination of Marius Van Der Merwe or Witness D as he was known in the Madlanga Commission.
He says three persons of interest have been identified and one has already been questioned as part of the ongoing investigation.
Van der Merwe was shot and killed in front of his family in the driveway of their home in Brenthurst, Brakpan, east of Johannesburg, on Friday evening.
