The woman driver recently killed by police in DC for trying to get past security barriers was reported in some stories as having the delusion that President Obama was communicating with her in some secret manner. As I understand the technical definition of delusion, it is a false interpretation of ordinary physical events with some personal significance. It is not a belief in physically impossible events or a hallucination, which is the sensation of unreal things such as hearing voices. It's popular to speak of people who have unusual political beliefs, conspiracy theories etc. as "delusional", but I don't think the psychiatric definition of "delusion" applies to beliefs that don't have some personal significance to the patient. I can see that people who hallucinate might often pose a danger to others or themselves. I wonder how many of the people in the recent headlines as shooters or being shot had hallucinations, vs how many had delusions vs how many had neither.