A legal malpractice claimant needs to show: 1. An attorney-client relationship with the lawyer; 2.Generally speaking, in the US, an opposing attorney does not owe you a duty that would give rise to a claim for legal malpractice. Legal malpractice cases are two cases in one. You must prove that your attorney exhibited negligence while handling your case. What should you do if you believe a lawyer has acted unprofessionally? This pamphlet offers guidance in answering questions. Unlike most law firms, we routinely file lawsuits against lawyers and prepare expert affidavits in support of legal malpractice claims. Limiting Liability and Settling Malpractice Claims. What do I have to establish to bring a malpractice lawsuit against an attorney in Minnesota?