Sippel was born in Jefferson City, Missouri.

He lived in St. Louis, Missouri and practiced law there, except for a period when he was an administrative assistant to Representative Richard A. Gephardt from 1993 to 1995.

On May 15, 1997, Sippel was nominated by President Bill Clinton to serve as a United States district judge of the United States District Courts for both the Western and Eastern District of Missouri, to a seat vacated by Judge Stephen N. Limbaugh Sr.

[2] He served as chief judge of the United States District Court for the Eastern District of Missouri from January 4, 2016,[3] to December 16, 2022.

[4] In spite of his joint appointment, Sippel maintains chambers and hears cases only in the Eastern District of Missouri.