Sir Jeffrey Donaldson has pleaded not guilty to 18 alleged offences.
The charges include one count of rape and allegations of indecent assault and gross indecency between 1985 and 2008, involving two alleged victims.
Lady Donaldson denies five charges relating to aiding and abetting his alleged offending.
The court heard evidence via video-link from Dr Christine Kennedy, a consultant psychiatrist.
She has examined Lady Donaldson and has written two reports, the most recent having been completed just days ago.
Dr Kennedy said Lady Donaldson is in no fit state to instruct her lawyers, follow proceedings or give evidence.
Prosecutors have proposed that that Sir Jeffrey Donaldson face “a standard trial”, opening next Tuesday, while “simultaneously”, his wife faces the trial of facts.
The judge heard legal submissions on the issue.
He will rule on Thursday on whether the trial of facts should run alongside the trial of Sir Jeffrey, or as separate proceedings at a different time.
