Is it legal for cop to shoot a man in the back with a taser when he has already given up?

I was accused of 1st degree armed robbery and misdemeanor theft on 6/3/11. Took to trial but prosecutor dropped the charge of robbery and settled for theft. But, the money as evidence was not on my person. Niether was there any evidence of a gun. There was never a gun or a theft. I was not even aware of what the cops were pointing guns at us ( Billy Wagner, Dakota Paulson and I) for. I still have nerve damage. Numbness and sensitivity to cold on hands. Painful to touch cold.