The physician's agreement to treat the patient would serve as proof of this relationship. Breach of duty means that the medical treatment from the doctor fell below the standard of care the patient could reasonably expect. Standard of care generally means a physician's conduct is judged in comparison with that of similarly trained professionals in the United States. The third element, the patient's injury, may be obvious and therefore not difficult to prove. More difficult to prove is the fourth element, that the injury is directly related to the physician's negligence.
Various states have specific statutes governing medical malpractice claims.
Many states provide for peer review by a panel of doctors before the claim may be reviewed by the court. Certain notice and time requirements may apply to your claim. If you believe that you have suffered injury due to the negligence of a physician, consult with an attorney familiar with medical malpractice law.