SAN FRANCISCO — California State Bar officials confirmed Thursday that they have secured a criminal immunity deal with a key witness in their misconduct case against Del Norte district attorney Jon Alexander that will enable them to take testimony on an alleged improper conversation Alexander had with a represented defendant.

Prosecutors claim Alexander has engaged in a host of misconduct during his tenure as DA of the tiny county, including the alleged conversation with a represented defendant in a drug case outside the presence of her counsel. Michelle Taylor wore a wire during the meeting, and the tape of the conversation has been entered into evidence in the bar’s case against Alexander. Alexander and his defense counsel, Kurt Melchior of Nossaman, say the bar has wrongfully accused a good man who is unpopular because of his status as a former methamphetamine addict.