Sydney man allegedly drugged his wife so he could rape his young stepdaughter.

Warning: This post describes a case of child abuse and may be triggering for some readers.

A “tired” working mum never considered the possibility her husband was drugging her at their Sydney home so he could sexually assault her daughter, a jury has heard.

The woman, who can’t be named for legal reasons, on Thursday said she noticed “powdery substances” in drinks made by her husband and she would suffer “extreme and sudden tiredness” that led her to seek medical tests.

“You just reassured me I was tired … I trusted you and I believed you,” she said at the Downing Centre District Court during her cross examination by the accused.

“I would ask you ‘have you put sugar in it?’ and you would say ‘no I haven’t done anything’… (but) it would taste different to when I made the drink.”

The 45-year-old man is representing himself after pleading not guilty to drugging his wife and stepdaughter.

He has pleaded guilty to 99 charges relating to the sexual abuse of his stepdaughter which started when she was 12.

A doctor told the jury the girl said her stepfather would crush travel sickness tablets to mix in her mother’s food and drink, and when she fell asleep he would sexually abuse the stepdaughter.

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A meat tenderiser found in the home had a small amount of white powder on it that was found to contain three different drugs.

“At any stage did you think… that someone, probably your husband, was drugging you?,” the accused asked the woman.

“No, I didn’t… you would always throw me off the scent,” she said.

The woman said she raised concerns about her husband’s close relationship with her daughter – whispered arguments, early morning walks on the beach and long gym sessions.

On one occasion she told him to “stay the f*** away from my daughter.”

“I was angry about the way you were behaving towards her,” she said.

She denied she was jealous of their close relationship.

The court previously heard SD memory cards discovered in the lining of the stepfather’s jacket contained 78 videos and 778 images which showed him sexually and indecently assaulting the stepdaughter, and in some of the footage she appeared to be asleep.

The mother said she found another SD card in her desk that she thought had family photos on it.

“But it didn’t. It had photos of you assaulting my daughter,” she said on Thursday.

The trial continues.