It varies from state to state, but the principles remain the same. The attorney must have spent seven (or ten) years as a "second chair" assistant to a death-qualified lawyer on death penalty trials. To be eligible to do that, s/he must have spent seven (or ten) years trying complex, felony criminal trials. I'm not sure which body governs and assesses whether or not a trial is considered to be complex; I only know that some are not. There are fewer and fewer attorneys who are death-qualified anymore, so much so that some counties only have one or two, and there are many convicted people waiting as much as twelve years (!!!) to get action on an appeal. It's ridiculously slow.