Judge Grimm had a distinguished military career and currently serves as a Lieutenant Colonel in the U.S. Army Reserve. His civilian career began in 1980, when he joined the State's Attorney's Office for Baltimore County, Maryland as an Assistant State's Attorney. A year later, he became an Assistant Attorney General for the State of Maryland, where he remained until 1984. From 1984 until 1997, Judge Grimm worked in private practice. On February 5, 1997, Judge Grimm was appointed a United States Magistrate Judge for the District Court for the District of Maryland. He received the Maryland Bar Foundation 2001 Professional Legal Excellence Award for the Advancement of Professional Competence, and the Maryland Institute for the Continuing Professional Education of Lawyers Distinguished Service Award in 1998. Judge Grimm has also written numerous books and articles on evidence, procedure and trial practice, and is an adjunct faculty member of the University of Maryland and University of Baltimore Schools of Law.