I remember hearing someone make the claim that Paul had been a member of the Sanhedrin prior to his conversion to Christianity. Is there any evidence for this claim? If so, what is it?
Stephen was stoned by the Sanhedrin and Paul (then named Saul) was present. The full story is told from Acts 6:8 to 7:60 but the relevant verses are:
(6:15 also shows they were in the Sanhedrin.)
And Paul's presence is shown in 7:58b:
Final note: in Acts 23:6 Paul himself appears before the Sanhderin and calls himself a "Pharisee".
This site seems to answer your question. I dont have any specific insights myself, and would have posted this as a comment, but dont have the rep to.