Katherine Helene Panin, 81, died on October 12, 2015, at a family home in Red Hill.

The jury was told on Monday that it was Ms Beowulf, 61, who called authorities, and that when they arrived they found Ms Panin at the foot of the back stairs.

Ms Panin had moved into the Red Hill home with her son Thorhammer Beowulf, his wife Ms Beowulf and their four sons.

Also living at the home was Mr Beowulf's de facto wife and their son.

The family had lived together since the late 1990s, the court heard.

Mr Beowulf, a bonsai artist, died in August 2015.

Prosecutors said Ms Panin was a wealthy woman who owned $2.6 million in money and assets. The Crown will allege the three accused had a financial motive to murder Ms Panin.

Ms Beowulf and her sons Thorsten Halley Beowulf, 32, and Bjorn Torin Beowulf, 31, were arraigned in the ACT Supreme Court on Monday. Each pleaded not guilty to murder.

Earlier, 35 potential jurors had asked to be excused from jury duty.

Chief Justice Helen Murrell granted several requests for jurors to be excused, for reasons including ill health and study.

Later, another 23 potential jurors were challenged by the Crown and defence until a final 16 were selected.

The trial is estimated to go for six to eight weeks, during which time the jury is expected to hear from 93 Crown witnesses.

Prosecutor Margaret Jones will make an opening address on Tuesday.