Headscratchers / Sherlock S3 E3 "His Last Vow"

• If it becomes known that Magnussen has all his blackmail material in his head with no physical proof, then he is rendered impotent. People would sue him for slander if he made his claims without proof. He might cause Mary problems if he let her background be known especially if certain foreign agencies took interest but Sherlock really didn't need to shoot him. Just inform Mycroft and either he or the CIA could handle the problem without repercussions to Sherlock.