Cadillac Repair: trunk brake lights, seville sls, failure points

Question
the trunk lid brake lights on my 96 Seville sls are only working on the passenger side what could cause this?

Answer
Ron,
Since the lamp circuit is not split until the trunk, the fault must be in there. Most common failure points on your car are the bulb sockets themselves so that's where I'd start looking. The actual connections in the sockets fail. It's also quite possible that the harness is damaged but my money is on the sockets