How do you open a broken trunk with no rear seat access?

If you have a back seat, then you do have access to the trunk. Most back seats come out fairly easy. The bottom usually just clips in. On each side about between your legs if you were sitting, right above where the seat touches the floor, push straight back 1/2 to 3/4 of an inch and lift up. Do this on both sides and lift the seat out. There should be 2 or 3 clips that goes up behind the back. The back should have a bolt on each side at the bottom outside corners. Take the bolts out and lift straight up and out. Now you can use a long extension and socket to remove the lock mechanism. On many newer cars, there is an inside trunk release you can pull so you can not be car jacked and locked in the trunk.