An Illawarra man stands accused of opportunistically sexually abusing two young girls over the course of a decade during neighbourhood gatherings, a court has heard. Kenneth MacDonald, 73, is fighting the allegations in a Wollongong District Court trial in which he has pleaded not guilty to 12 child abuse charges stemming from the 1980s. The Crown case against the pensioner, who used a hearing loop as he sat in the dock, was aired by prosecutor Nerissa Keay on Monday. It's alleged MacDonald would isolate himself with the complainants, often when they were sleeping, or by calling them from the street into his garage. The first complainant alleges the abuse began when she was aged four and that "almost every interaction" with MacDonald involved him either touching her breasts, back, between her legs, or vagina. It's alleged the abuse got worse as she got older. On one occasion, MacDonald allegedly approached the girl from behind while she was wearing a swimsuit and inserted his fingers into her vagina, causing pain. Years later, he allegedly grabbed the girl's breast over her shirt, leaving a "greasy" hand print stain on it. MacDonald allegedly forced both complainants, who had been asleep in a bedroom during a barbecue, to touch his penis in 1980. The first complainant disclosed the alleged abuse in 2020, prompting an investigation. Police approached the second complainant who provided a statement detailing similar alleged indecent assaults, as well as four separate occasions where MacDonald allegedly forced her to perform oral sex in his garage. During a neighbourhood barbecue held at his home, MacDonald allegedly entered a room in which the girl was sleeping in before he digitally penetrated her. After the complainant disclosed the allegations, she on two occasions revisited MacDonald's home with a recording device attached to her and questioned him. He denied touching either complainant. He also later denied the allegations in a police interview following his arrest. Defence barrister Ben Clark urged the jury of 12 to not leap to a certain view, asking them to remember MacDonald continuously denied the allegations. The issue the jury must preside over during the trial is whether the alleged incidents ever happened. One of the complainants gave evidence in a closed court on Monday afternoon. The trial, before Judge Andrew Haesler, continues and is scheduled to run for over a week.