During the trial at Sydney Downing Centre, a jury heard the 45-year-old salesman allegedly drugged his wife with travel sickness tablets in order to sexually assault her daughter.
The mother told the court how she would experience "extreme and sudden tiredness" at home and began to notice a bitter taste in her drinks and food. She also spotted "powdery substances" in drinks made by her husband.
During her cross-examination by the accused, who is representing himself, the woman said: "You just reassured me I was tired ... I trusted you and I believed you.”
"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,” she added.
According to AAP, a doctor told the jury that the accused would crush tablets into the mother’s food and drink.
The man allegedly crushed up the tablets using a meat tenderiser, which was found in the home with traces of three different drugs.
The court also heard that SD cards were found in the stepfather’s jacket with 78 videos and 778 graphic images depicting him indecently assaulting the girl.
The man has pleaded not guilty to 22 counts of allegedly drugging the girl and not guilty of five counts of drugging the mother.