He was an Assistant United States Attorney for the District of Wyoming from 1930 to 1933.

[1][2] During World War II, he served in the Allied Command in Italy and became head of the legal division in that region.

[2] On October 22, 1955, Kerr received a recess appointment from President Dwight D. Eisenhower to a seat on the United States District Court for the District of Wyoming vacated by Judge Thomas Blake Kennedy.

Formally nominated to the same seat by President Eisenhower on January 12, 1956, he was confirmed by the United States Senate on March 1, 1956, and received his commission the following day.

Courthouse in Casper, Wyoming, was named in Kerr's honor.