The Swinger Who Swung by the Neck
(1970)(A book in the Gibby Gibson series)
A novel by Hampton Stone (Aaron Marc Stein)
An intriguing, suspenseful Mystery about an assistant DA who tries to help out a mathematical pot-smoking genius who gets mixed up with gangsters: "Through the good offices of a friend of a friend, Jeremiah X. Gibson and his first name colleague, Mac, both of the New York D.A.'s office, quite innocently get embroiled in drug running and murder."
Used availability for Aaron Marc Stein's The Swinger Who Swung by the Neck