Vincent O’Dempsey confessed to McCulkin murders, Brisbane court hears

Brisbane man Vincent O'Dempsey allegedly told three separate people that he was involved in the 1974 murders of Barbara McCulkin and her two daughters, a court has heard.

Mrs McCulkin and her children Vicki, 13, and Leanne, 11, have not been seen or heard from since January 16, 1974.

The trio are alleged to have left their Highgate Hill home with the 78-year-old and his associate Garry Dubois in a distinctive orange Charger.

Prosecutor David Meredith told the Brisbane Supreme Court today that Mr O'Dempsey admitted to three separate people he was involved in the subsequent murders of the women.

The witnesses were a person he was growing cannabis with in the late 1990s, a lover from the 2000s and a fellow prisoner in January 2017.

Mr Meredith said the witnesses were unconnected other than they were all involved in criminal circumstances.

"They were people who you'd might expect Mr O'Dempsey to trust that they would not speak to police," Mr Meredith said.

Mr O'Dempsey's trial before Justice Peter Applegarth is expected to take up for four weeks.