Medical malpractice cases are  the most difficult cases to win.  That is primarily because most all of them require an expert witness to testify that the defendant doctor failed to meet the standard of care set by other doctors.  Often the defense can find a witness to say the doctor met that standard.  There are three main exceptions to the requirement of an expert to testify there was malpractice.  1).  Cases where the courts have held the situation is so simple and obvious, the jury can figure it out on its own.  Think of a sponge or clamp being left behind.  However, courts are reluctant to recognize that exception.  For instance, in California leaving a tube  is thought to require an expert to say there was negligence.  2).  A doctor unreasonable abandoning a patient may not require an expert.  3).  A doctor failing to advise the patient of  material risks may not require an expert.