"Delusional disorder is a psychiatric diagnosis denoting a psychotic mental disorder that is characterized by holding one or more non-bizarre delusions[1] in the absence of any other significant psychopathology. Non-bizarre delusions are fixed beliefs that are certainly and definitely false, but that could possibly be plausible, for example, someone who thinks he or she is under police surveillance. In order for the diagnosis to be made, auditory and visual hallucinations cannot be prominent, although olfactory or tactile hallucinations related to the content of the delusion may be present."
YUP..he definitely fits the definition.
