Under Massachusetts law, a patient may refuse treatment, and the burden is on the physician to obtain informed consent from the patient for any medical treatment or procedure.  A person can give informed consent only if she has been provided with all relevant information about a proposed treatment (such as possible outcomes, side-effects, and alternative treatments) and has the capacity to consent (to understand the information given to her and to communicate her preference). If a doctor performed a procedure on a patient without first obtaining informed consent, then he or she might certainly be vulnerable to a medical malpractice claim.
 
There are only a few situations in which informed consent is not required from the patient, such as: (1) If the patient is unconscious and there is an emergency situation (as is often seen in medical dramas); (2) If the physician reasonably believes that disclosing certain information might harm the patient; and (3) If the patient is incapacitated but an authorized representative, such as a guardian or health care agent, has been properly informed and has consented to the treatment.