[1] Slattery appeared in such films as A Distant Trumpet, The Boston Strangler, Walking Tall, The No Mercy Man and Herbie Rides Again.

Born in New York, Slattery was a graduate of All Hallows High School who briefly studied at Fordham University, where he had scholarships in track and football.

He left Fordham and enlisted in the United States Army Air Forces during World War II, serving as a lieutenant in the Pacific for two and a half years.

[2] Slattery was distinguished by a square-jawed look and a rough, gravelly voice that made him ideal as a "tough guy" character, usually as a cop or a drill sergeant type.

Slattery was a familiar face on series television during the 1960s thru the 1980s, appearing in numerous guest roles including Route 66, The Alfred Hitchcock Hour, 77 Sunset Strip, Gunsmoke, Rawhide, The Andy Griffith Show, Bewitched, The Invaders, F Troop, The Green Hornet, The Virginian, Bonanza, The Partridge Family, The Odd Couple, Owen Marshall: Counselor at Law, The Mod Squad, Emergency!, Run, Joe, Run, The Waltons, Ironside, Kojak, The San Pedro Beach Bums, and Knight Rider.