You are a doctor. One of your patients, whom you have diagnosed as HIV positive, is about to receive a blood transfusion prior to being released from the hospital. He has told you, in the confidence of your doctor-patient relationship, that after he gets his transfusion, and his medicine from you, he intends to infect as many people as possible with HIV starting that evening.
Because you are bound by doctor-patient confidentiality, there is no legal way to stop this man from carrying out his plan. Even if you warned the police, they would not be able to arrest him, since his medical information is protected.
You know that you could change his blood-type in the hospital's computer which would result in his receiving the wrong blood-type.
Is it appropriate for you to change this man's blood-type in the computer, thereby killing him, in order to prevent him from spreading HIV?