While she didn't see who her attacker was, she heard him call her a "b****", and recognised her son's voice, the court heard.
Archer is then alleged to have beaten Mr Eaton with the axe handle and also attacked him with a pair of scissors, and another unknown sharp object.
The attack suddenly stopped when Archer demanded money, Crown prosecutor Barnaby Hawes told the jury in an opening statement today.
Archer is then accused of driving away in Mrs Geary's car with $1000 in cash, Mr Eaton's wallet, and a DVD player.
The couple received fractured bones and bruising.
Archer was picked up by police in a Christchurch park four days later.
Mr Eaton died some six months later, but a statement he gave police will be read to the jury during the trial, which is set down for 3-4 days.
Archer denies charges of burglary, theft, and causing grievous bodily harm to both Mrs Geary and Mr Eaton.
Defence counsel Brian Callaghan told the jury that Archer denies assaulting his mother. The defence position is that it was in fact Mr Eaton who had attacked Archer that day. And while that was happening, someone else had entered the house and "attacked his mother without his knowledge".
Mr Callaghan said Archer had not broken in, but had been let in.
He told the jury that it was up to the Crown to prove that when Archer entered the property he did so with intent to commit a crime.
The trial, before Judge Alistair Garland, continues.
