You can complete a complaint form online or download a PDF complaint form from the State Bar's website. If malpractice seems evident, the client can then choose to file a lawsuit against the original attorney.Once you've decided to take your grievance about an attorney to the State Bar, you need to file an attorney complaint form. First of all, you can't sanction opposing counsel, only the Court can "sanction. " Next, you don't "have" the preponderance of evidence. Legal malpractice cases are two cases in one. You must prove that your attorney exhibited negligence while handling your case. The general rule is simple: Non-clients generally cannot sue lawyers who did not represent them. Yes, you can sue your attorney for legal malpractice if you believe they acted negligently and caused you harm. To bring a claim for legal malpractice against an attorney in California, you must establish the four key elements covered in this article.