How do I find out a lawyers success rate in the courtroom?
A lawyer's courtroom record is not so easy to analyze as wins and losses. For instance, there are a number of times in a civil litigator's career where the job isn't to win some money or keep the other side from winning any money. A lot of times, civil litigators will only consider it a win if they get a verdict above a certain amount of money, or if they get a verdict below a certain amount of money, depending on which side they represent.
Likewise, with criminal lawyers, sometimes the goal is to convince the jury not that the client is innocent, but that they aren't guilty of a serious crime like rape or murder. So if the client is charged with capital murder (the prosecution wants the death penalty), and the jury returns a verdict of manslaughter, the defense attorney arguably "won." But that wouldn't be clear from court records.
The best thing you can do is call a few lawyers and ask for a referral, or ask about a specific lawyer. Lawyers know each other, and they know who is good and who isn't.