How can a medical facility prove that a patient has consented to the disclosure of medical information?

by showing that the patient has signed a consent form  

Explanation:

The consent form is a document that allows the patient to expressly express their willingness to consent to the performance of a certain procedure, after clarification provided by the doctor, assuring him the right to decide on the treatment proposed by the responsible professional.

This document must be signed by the patient proving that he has authorized the procedures. For this reason, we can state that if a medical facility needs to prove that a patient has consented to the disclosure of medical information, the facility must show that the patient has signed a consent form.

when comparing the cases, what similarities are there in the cases that suggest one person committed these murders?