He claims the Boeremag members, found guilty of treason, are seen consulting their lawyers in jail.
Retired Captain Deon Loots testified that his estranged wife, crime intelligence officer Colonel Miranda Loots, had kept him informed of developments in the Boeremag trial after he left the police in 2000.
"Just after the first arrests she already told me they were listening in on the cells at C-Max [prison in Pretoria].
"In about 2007, she told me how advanced crime intelligence was, how they knew everything that was going on in the court cells, what the legal representatives discussed with the accused, and how they could hear and see everything that went on around the court case," he said.
Loots was testifying in an application for a special entry on the court record, which could eventually be used on appeal in an application to set aside the treason convictions of the 20 Boeremag members.
Loots said his wife showed him footage of the accused, displayed on screens at crime intelligence's "war room", and also of the accused talking to their lawyers.
Loots testified he had refused to make a statement in the trial because he was upset about the way in which the coup plot was orchestrated.
He used to be the police handler assigned to police spy JC Smit, one of the chief witnesses for the state in the Boeremag treason trial.
He testified that he had kept in contact with Smit even after deciding to leave the police in 2000. He introduced Smit to another handler when both of them were asked to make statements just before the first arrests in the case.
Loots said he had repeatedly refused to make a statement, despite pleas by his estranged wife, Loots, and two of the unit's top officers.
This was because he did not agree with "the way in which the whole thing was being orchestrated and driven".
He was of the opinion that the whole thing was a "power struggle" between two of his superiors.
He and Smit at one stage went to see an attorney and an advocate for advice. Loots was told he would not be in trouble if he refused to testify, but that Smit was in a more difficult position.
At some stage, said Loots, he went to see the prosecutors in the case, who told him not to come near the court or any of the accused, because he was still under an oath of secrecy.
Loots said he had decided "the truth must come out" after working in India in 2011. When he returned, he attended the Boeremag trial for the first time, but claimed the investigators warned him to stay away.
He claimed some of his former colleagues threatened him and told him he was under oath not to reveal any information about the Boeremag case.
The matter would continue on March 11. Defence lawyers said they intended calling two more witnesses to back up Loots' evidence. The state, for its part, said it would call at least 10 witnesses to refute Loots' claims. – Sapa