I would like to have my record expunged

I was charged with less than 1/2 oz poss and sell in 1990, the officer that arrested me is no longer on the force because at the time he was doing illegal wire tapping, and several cases were removed due to this fact. I did not receive money from the officer I was asked to get this as a favor. I have had 0 on my file in over 25 years. and this is not even a felony now.