"VINCENT O'Dempsey did it".

Those words were heard during a committal hearing in Brisbane yesterday for two men accused of murdering Barbara McCulkin and her two daughters, aged 13 and 11, in January 1974.

Two men have been charged over the cold case murders; Warwick man Vincent O'Dempsey, 77, and Torbanlea man Garry Reginald Dubois, 68.

Mr Dubois's brother Paul gave evidence on Monday about how his brother claimed he was not there when Ms McCulkin and her daughters disappeared.

Paul Dubois told the court he spoke to his brother about it and that his brother told him about a conversation he had had with Mr O'Dempsey.

The court heard his brother had been told by Mr O'Dempsey that "the kids weren't meant to be there" and that Mr O'Dempsey wanted to kill Barbara because she had evidence on him that "would have got him around 20 years (in jail)".

When asked about the phone conversation he had had with his brother, Paul Dubois said he could not remember it perfectly word for word but "the gist of it was that he said he had nothing to do with it, he wasn't there and that Vincent O'Dempsey did it."

Paul Dubois said he had not spoken to his brother for about 21 years after they'd had a falling out following a family dispute.

Warwick man Warren McDonald also gave evidence on Monday about a conversation he'd had with Mr O'Dempsey while they cultivated marijuana on a property near Warwick. Mr McDonald said he was in a car with O'Dempsey talking when Mr O'Dempsey told him "you need another notch on your gun" and Mr O'Dempsey then confessed to killing the McCulkins.

Mr McDonald also told the court he avoided jail time for drugs charges and a confiscation order for coming forward with this information.

Barbara and her daughters, Vicki and Leanne, vanished from their Brisbane home on January 16, 1974.

The court heard about 87 witnesses were involved in the case.

It is expected the committal hearing will continue until Friday and possibly next week.