Susan Blyth Neill-Fraser, 55, has pleaded not guilty to murdering her partner, whose body has not been found.

Mr Chappell, 65, was the chief radiation physicist at the Royal Hobart Hospital's Holman clinic.

He was last seen on January 26, 2009, on board his yacht, Four Winds, which was moored off Sandy Bay.

At a directions hearing yesterday, Justice Alan Blow said a jury would be empanelled on Tuesday, with opening submissions to begin later that day.

Ms Neill-Fraser's lawyer, David Gunson, SC, said he expected the trial to take three to four weeks.