A backseat
DUI occurres when a sober person is driving an intoxicated person home, and the intoxicated individual is giving the driver shitty directions, and false instructions to turn, and then saying "No, No, not this street..."
This causes the driver to
speed up, slow down, and begin to turn, then swerve back into the driving lane, leading others observing the vehicle from the outside to believe that the driver is
DUI.
"I was driving Marcus home the other
night from the local water
hole and he kept telling me to turn and shit and I was all over the place and then I got pulled over, but it was cool, the
cop realized Marcus was just backseat DUI."