Crown prosecutor Robin Bates opened the Crown case yesterday and foreshadowed the evidence each girl was likely to give during the trial.
He said they would tell the court of a scenario where all four of them were on the man's bed at once.
"It appeared to be a situation where there was abuse taking place and the girls were being asked to change places," Bates said.
"He would say something along the lines of 'next', and those young girls would have to change place."
Some of the alleged sexual assaults also took place after the girls had showered.
Bates said the defendant would tell the girls to lie on a towel on the floor and he would cover them in baby oil or powder and indecently touch them.
"I felt like this happened quite frequently," the first complainant told police.
Her video interview was played for the jury yesterday during which she recalled seeing the defendant raping another girl while filming it.
"I thought it was weird and wrong," she said.
"I just stood there by the camera and I remember just watching it happen."
The complainant - now an adult - said the man was always watching pornography and would show it to the girls.
He allegedly swore them to secrecy.
"We couldn't tell anybody about this. This was our secret. That's what [he] told me,'' she said.
"Being in the situation I've been in, I feel he's got such a sick mind."
She was asked by police what was said by the defendant at the time but she could not remember.
"He was just laughing away, thinking he was having the time of his life," the complainant said.
Another of the girls who was allegedly abused would tell the jury she got upset on one visit to the house and wanted to go home.
"He said he would put her outside in the dog kennel and leave her there," Bates said.
The defendant's partner was the first witness called by the prosecution yesterday.
She spoke about the different places in Central Otago in which they had lived and how her work left him at home alone frequently.
She was unaware of anything untoward happening in any of their homes, his partner said.
The man did own a camera, the witness said, and she told the court he had used it to film them in the bedroom and occasionally the bathroom.
It was used for no other purpose, as far as she knew.
The trial before Judge Michael Crosbie and a jury of seven women and five men is due to run for six days.
