Mark has been a partner in Campagnoli, Abelson & Campagnoli since 1981, with an emphasis on professional malpractice and, in particular, plaintiffs' legal malpractice. He has successfully tried, arbitrated, and settled numerous legal malpractice cases. Mark has lectured to various attorney groups on legal ethics, significant case law developments, and other topics pertaining to legal malpractice. He is a past chairperson of the Bar Association of San Francisco Legal Malpractice Committee and has served as an expert witness in legal malpractice cases. Mark serves as a mediator and arbitrator for the San Francisco Superior Court. He has been previously named to the Northern California Super Lawyers list and as an Outstanding Lawyer of America.