The script held in the Crawford Collection in the AFI Research Collection contains the following character notes (excluding regular characters):
'SAMMY WALKER: Must be big and strong-looking, perhaps even slightly flabby. Late twenties, early thirties. Sammy has suffered brain damage and has the mentality of a 10 year old. He always wears his cloth cap. It would help if the actor had a partial plate. (IF NOT, BLACKEN A COUPLE OF TEETH) One can see a few gaps when Sammy smiles.
'PRIMROSE TAYLOR: Policewoman who comes into Homicide. Twenties. Must be attractive. A knowledge of judo would help.
'BEN WALKER: Sammy's brother. Older. Ben looks after Sammy, treats him almost like a son. [Note: an annotation to this character note in blue ink specifies that Ben is five years older than Sammy.]
'JANINE FISHER: Young, attractive air hostess. Killed in first commerical.
'BEV ADAMS: Janine's room mate. Same age, same job.
'DR. ALCOTT: Doctor at post mortem.
'JIM HARRIS: Private detective.
'CAPTAIN RICHARDS: Airline pilot. [Note: an annotation to this character note in blue ink reads, 'needs to be good'.]
'OLD LADY: Old lady on bus.
'MARY WALKER: Ben's wife.
'MRS. FENTON: Very attractive, long blonde hair. She is not provocative in her attitude.
'SALLY GREEN: Young, attractive, ballet teacher. Second murder victim.
'MR. PHILLIPS: Late thirties, early forties. Obscene phone caller.
'AMBULANCE MEN: Actuals.
'SMITH: Interviewed at airport.
'POLICE SERGEANT: One scene.
'STUDENTS IN BALLET SCHOOL: Actual.'