Born in Highland Park, Illinois, Decker received an Artium Baccalaureus degree from the University of Illinois at Urbana–Champaign in 1926 and a Bachelor of Laws from Harvard Law School in 1929.
He was a law clerk to a Judge of the Illinois Appellate Court from 1944 to 1948.
[1] Decker received a recess appointment from President John F. Kennedy on December 12, 1962, to the United States District Court for the Northern District of Illinois, to a new seat authorized by 75 Stat.
He was confirmed by the United States Senate on March 28, 1963, and received his commission on April 2, 1963.
His service terminated on November 3, 1993, due to his death in Chicago, Illinois.