The murder trial of musician Molemo "Jub Jub" Maarohanye and co-accused Themba Tshabalala resumes in the Protea Magistrate's Court on Monday.
Video expert Riana Smalberger is expected to give evidence on whether the cellphone video footage presented by the State earlier in the trial had been tampered with.
On Wednesday, Smalberger called by Maarohanye's defence, came under fire.
She had told the court she found 13 video clips on a cellphone, 10 of them were deleted and two were still on the phone.
State prosecutor Raymond Mathenjwa wanted to know what had happened to the missing videos and Smalberger replied that she had made a mistake, and that only 12 videos were found.
She told the court she started working on the video only on Tuesday, when her brief was to download it. That was why she had not made any analysis.
Mathenjwa accused her of being in possession of private information not relevant to the trial.
He said she was supposed to analyse the two video clips and was not supposed to retrieve deleted information from the phone. He was not clear on why she had failed to make an analysis.
Smalberger said she had been on leave and had only a preliminary report, which she was unable to testify about until a full report had been completed.
Maarohanye and Tshabalala face charges of murder, attempted murder, and driving under the influence of alcohol and drugs.
They were allegedly racing their Mini Coopers when they crashed into a group of school children in Mdlalose Street, in Protea North, on March 8, 2010.
Four boys died and two were seriously injured.