'94 Toyota camry - won't start

Unlikely. Is there some master fuse in a

Could be a dead battery but it could also just be a bad cable or battery post connection, although I would have expected the mechanic to catch that. You may even have a current drain running it down.

Start with the simple stuff. To check the battery post connections turn on the head light switch. Dig a screwdriver in between the post and the clamp. If the lights come on you found the problem. Otherwise wiggle the heavy cables going to the starter and to ground and see if the lights come on. You say that nothing else works like the interior lights or radio, right?

Dead battery is likely it, bad cables wont help, never keep a battery testing weak, charge it and go back to the mechanic.

Sounds like the battery went bad to me.

Check the battery terminals, if loose tighten. If that doesn't help, just get a new battery -

Is the headlight switch off or on? The headlights are supposed to shut off when the ignition is off and the drivers door is opened. If the headlights are in the "on" position and the drivers door switch sticks (off) the headlights will run the battery down. If your dome light stays off when the drivers door is opened then you know this may be your problem. I know this from experience.