Person 17, who is at the centre of an allegation of domestic violence, which Ben Roberts-Smith denies, will enter the witness box

The woman with whom Ben Roberts-Smith was having an affair - and who is at the centre of an allegation of domestic violence against him - is expected to give evidence in his defamation trial Tuesday afternoon.

The trial has spent weeks focused on Australian SAS missions in Afghanistan, with a series of former comrades giving evidence about actions on operation, but it will shift its focus to Australia as the woman, anonymised in court documents as Person 17, to enter the witness box.