There should be a tool in the toolkit that manually operates the front and rear latches. The front latches are operated through those small covered holes in the header panel (behind the sunvisors).
The rear ones operate through slots in the front trim panel in the trunk. It should show where most of this is in the owners manual.
The mechanic should be capable of retreiving fault code and actual values through the control module diagnostic port, if not, you need to find a shop which has this equipment.
If all the latches are found to be fully locked, then the diagnostic port may be the only efficient way to find out which switch is defective, unless you mechanic wants to go through each switch individually and test them. He could do this easiest at the connector at the control module which handles all the input signals. There may even be a stored trouble code (DTC) which will immediately indicate what switch or latch is defective.