JOHANNESBURG -  "He greeted me. Then he pointed a gun at me and said I should do what he said or I'll get hurt," the now 18-year-old told the court.

She was testifying in the trial of Johannes Jacobus Steyn, who has been called the "Sunday rapist".

He has pleaded not guilty to two counts of murder, 11 of rape, 10 of sexual assault, 10 of kidnapping, one of attempted sexual assault, one of attempted kidnapping, and two of assault, all committed in 2008 and 2011.

The murder charges relate to the deaths of schoolgirls Louise de Waal and Lazanne Farmer.

The victim who testified on Tuesday that she and her sister were walking to a cafe in Rustenburg on March 7, 2010 when she was kidnapped at gunpoint and blindfolded.

She was driven to an unknown location where her attacker partially undressed her and touched her.

"He touched me and I pushed him away and I said he must leave me alone." He took her bra and hid it under the car seat.

She continued to describe how she was sexually assaulted.

Counselling sessions between Steyn and his employer were ruled inadmissible evidence.

Allowing this information to form part of the evidence this late in the trial might infringe Steyn's rights, Judge Sita Kolbe said.

Kolbe said she would give full reasons for her ruling at the end of the trial.

Earlier, pathologist Dorothea Joubert testified that no medical help would have saved Farmer.

"I doubt that, with the amount of brain injuries she had."

Joubert said Farmer died of head injuries. Her skull was fractured. There was blood in her nose, mouth and ears, and airway, indicating that she was breathing at the time she was injured.

These functions were likely to have been of peri-mortem nature, when the body was shutting down, Joubert said.

She said the injuries were typical of someone who had jumped, or fallen, out of a car.

Before court proceedings were postponed until Wednesday, a linkage analysis by Gerard Labuschagne was allowed.

Labuschagne, a doctor in psychology who specialises in serial offences, said the aim of a linkage analysis was to identify serial crimes committed by one offender.

In all 10 cases, where 11 white minor females were either abducted or attempts made to abduct them, a car and a firearm had been used.

In seven of the eight successful attacks, the attacker took items belonging to the girls. These seemed to be for souvenir purposes.

"The keeping of souvenir items, while not unheard of in serial offender behaviour, is uncommon," Labuschagne said.

His conclusion was that the successful kidnapping and rape cases in the trial were the work of the same offender.