https://drive.google.com/file/d/0B0s...w?usp=drivesdkSo my radio wasn't working and I let a friend try to fix it, my tail lights don't work now. The cut the harness but I'm not sure if that's the problem. What can the cause be I've tried checking fuses and replacing the lights. Also the blinkers and break lights work on both sides.

 

Looking at that picture, in this day and age, I still fail to understand why some people still cut the old radio connector in the dash. There are install kits to make it all plug and play.

If all this happened after your friend messed with the radio, I am suspecting something is shorting out or a wire was cut that shouldn't have been. I would start with inspecting everything your friend did. You may also want to actually test the fuses for the signal lights (I've seen some that look good, but were actually bad).