Senior police detective Frans Mathipa had been fighting for four months to gain access to a crucial piece of information in the case he was working on. Finally, he was told, it was going to come his way.

But he feared his pursuit of it could cost him his life. Two days later, his car was found overturned - he had been shot dead while driving.

Now seven members of South Africa's special forces, and one military police officer, have been charged with murdering Lt Col Mathipa, a highly respected officer, in August 2023. They deny the charges.

There has been no date scheduled for their trial, and there are concerns it will never go ahead, because three of the men charged with his murder have refused to comply with a court order revoking their bail. They are still working for the army's special forces, and one of them has been promoted.

The BBC World Service has been given exclusive access to the prosecution case against all the men. The case has caused consternation in one of Africa's most robust democracies, with fears the country's military is significantly overreaching its mandate.

We asked the South African army whether it was responsible for Mathipa's killing. It did not respond.

We have also interviewed key sources in the police investigation - South Africa's former head of counter-terrorism in The Hawks; Mathipa's commanding officer; and Mathipa's family - to build the most comprehensive public account of the events leading up to the detective's death. It presents a compelling case that South Africa's special forces are responsible for his murder.

In particular, police documents show that the vehicle that trailed Mathipa just before he was shot was registered to a front company for the special forces. And that tracking data found in that vehicle puts it at the scene of the shooting.

One of the men in the car, Maj Sunnybooi Wambi, the documents show, was also spotted at the scene of an alleged abduction carried out by special forces soldiers - the case that Mathipa had been investigating. After Mathipa's death, special forces issued a chilling warning to The Hawks, the police documents say.

" You can appoint 10 investigating officers; we will kill all of them," said the warning, according to police. Outside the UK watch on YouTube, externalThe case Mathipa had been investigating was sensitive.