Casual is the opposite of Religious. Religious is related to Minister. Minister is related to Official. 
Suspect is a type of Person. Suspect is related to Investigation. Examination is a type of Investigation. 
Casual <--Antonym--> Religious <--RelatedTo--> Minister <--RelatedTo--> Official 
Person <--IsA-- Suspect <--RelatedTo--> Investigation <--IsA-- Examination 