“Modus operandi – MO – is learned behavior. It’s what the perpetrator does to commit the crime. It is dynamic – that is, it can change. Signature, a term I coined to distinguish it from MO, is what the perpetrator has to do to fulfill himself. It is static; it does not change.”

“Modus operandi – MO – is learned behavior. It’s what the perpetrator does to commit the crime. It is dynamic – that is, it can change. Signature, a term I coined to distinguish it from MO, is what the perpetrator has to do to fulfill himself. It is static; it does not change.”

— John E. Douglas