The two-day hearing for Sub-Lt. Jeffrey Paul Delisle is scheduled to begin Thursday in Halifax provincial court.
But Dan Brien, a spokesman for the prosecution service, said Tuesday that the Crown will seek an adjournment until Jan. 31 because the lead prosecutor is unable to fly from Montreal due to a medical issue.
Defence lawyer Mike Taylor said he doesn't object to the application, adding that the Crown, defence and judge have discussed the matter.
"We notified (the judge) as soon as we realized there might be a problem," Taylor said. "We've had a couple of discussions among the three of us and between myself and the Crown to sort this out. So everybody is on board."
Taylor said it's still not clear whether Delisle will testify, but he added that he intends to call at least one expert witness to testify on the extent of the damage Delisle's action caused to national security.
Delisle pleaded guilty in October to breach of trust and passing information to a foreign entity that could harm Canada's interests.