While california legal malpractice law has evolved for over half a century and many nuances in the law and its application have developed over time the general principles that guide and govern the responsibility of an attorney to the client have remained virtually the same for example the attorney owes the client the basic duties of care loyalty condentiality and so on in. To prove legal malpractice in california the plaintiff must show an attorney client relationship existed the attorney was negligent in the legal representation provided the negligence proximately caused the client harm the extent of injury. According to california malpractice law a patient can file a medical malpractice claim up to one year after the discovery of the act that caused the injury or up to three years from the date that injury occurred whichever occurs first applies. California legal malpractice law offers practical guidance including effective claim prevention and loss avoidance two cases in one defending a malpractice case requires not only an understanding of legal malpractice law but the substantive law of the underlying the lawsuit or transaction