Dr. Koch was approached by Nina who was suffering from a very serious case of appendicitis. upon examination. Dr. Koch discovered that a surgery was necessary but the risk of death to Nina was high. This fact was made known to Nina. however Nina insisted that the surgery be carried out since the pain was unbearable. Dr. Koch proceeded with the surgery but Nina subsequently died in the operation room.

Explain the defence(s) available to Dr. Koch should he be charged for causing the death of Nina.