Mr De Wet, a supervisor on the farm, will testify that he was under duress when he was forced to throw their bodies into the pig enclosure, according to both the prosecution and his lawyer.
William Musora, 50, another farm worker, is the third accused. He and Mr Olivier, 60, are yet to enter a plea and remain behind bars.
Mr De Wet’s lawyers say he has truthfully disclosed what transpired on the night Ms Makgato and Ms Ndlovu were killed in August 2024.
Shortly after court adjourned on Wednesday, he walked out of the court as a free man and was whisked away by his lawyers, while Ms Makgato’s brother Walter Makgato sobbed outside the court building.
He told the BBC that the release of one of the men allegedly involved in the killing of his sister means justice will not be served.
Mr De Wet will be taken into protective custody until the end of the trial.
The case has caused widespread outrage across South Africa which has exacerbated racial tension between black and white people in the country.
This is especially rife in rural areas of the country, despite the end of the racist system of apartheid 30 years ago.
Most private farmland remains in the hands of the white minority, while most farm workers are black and poorly paid, fuelling resentment among the black population, while many white farmers complain of high crime rates.
The trial is set to resume on 6 October.