I'm voting for the wife also. Means, Opportunity. Motive.

Your wife, in the garage, with a hairpin.

Search her immediately. She may be hiding the hairpin in her mouth. Sarah Connor escaped from a mental hospital using only a paper clip. I saw it. That, and a syringe full of antifreeze, and a nightstick, and a cybernetic organism who had befriended her estranged son...