Born in Posen, German Empire, (now Poznań, Poland), Koscinski emigrated to the United States and received a Bachelor of Laws from the University of Michigan Law School in 1910.

He was a public administrator for Wayne County, Michigan from 1923 to 1936, and was a member of the Detroit City Pension Commission from 1934 to 1937, and then of the Michigan Public Trust Commission from 1937 to 1938.

He was a government appeal agent for the Selective Service Board from 1940 to 1945.

[1] On June 4, 1945, Koscinski was nominated by President Harry S. Truman to a seat on the United States District Court for the Eastern District of Michigan vacated by Judge Arthur J. Tuttle.

Koscinski served in that capacity until his death on November 21, 1957.