EVIDENCE heard in court revealed that the scene of the crash in which former president Nelson Mandela's great-granddaughter Zenani Mandela was killed could have been tainted and may have impacted the police investigation.

Her mother Zoleka Mandela was brought to tears upon hearing this at the Johannesburg Magistrate's Court yesterday. She had to be comforted by her mother Zindzi and grandmother Winnie Madikizela-Mandela outside the court.

Accident specialist Craig Proctor-Parker conceded under cross-examination in the trial of Sizwe Mankazana, the man driving the car in the crash that killed the 13-year-old girl, that the scene at the M1 and M2 interchange could have been partly "spoilt on the day" he visited it.

Mankazana, 25, has pleaded not guilty to charges of culpable homicide, reckless and negligent driving, and drunk driving.

Mankazana allegedly lost control of his father's car and hit a concrete barrier after a 2010 World Cup concert. Zenani died at the scene.

Proctor-Parker testified it was highly probable the driver was travelling at high speed and the crash was what would be defined as a "single vehicle loss of control".

"He lost control of the vehicle and hit the barricades, resulting in the car facing in an easterly direction."

However, under cross-examination by defence advocate Kenny Oldwage, Proctor-Parker said he used no assessment instruments and did not know what could have caused it.

"Are you saying you used nothing but the simple naked eye?" asked Oldwage and Proctor-Parker agreed.

"I found no [skid] marks that I could calculate," the specialist said before admitting that the scene was partly messed up and was not secured properly for him to make a proper evaluation.

Proctor-Parker also could not indicate how fast the car was going at the time of the crash.

Oldwage criticised him for relying only on the police docket to compile his report. The case continues.