Researching David Coombs

Coombs is best known for his research on Winston Churchill's art work, publishing two books on the subject (1967 and 2003). He has been described as "the official authority on Churchill's art." He produced and later revivised a catalogue which brings together all of Churchill's 500 or so paintings and 2 sculptures, in which each piece has been given a number prefixed with the letter C for Coombs. This catalogue also exist in the form of a digital archive of the paintings. His 1967 catalogue was described as "an indispensable catalogue" of Churchill's art.

Coombs spent twelve years on active duty service with the United States Army Judge Advocate General's Corps. During this time, he was an acting chief of military justice, senior capital defense counsel, and judicial advisor for the Iraqi Central Criminal Court, and was certified as a military judge.

He was professor of law at The Judge Advocate General's Legal Center and School (TJAGLCS) in Charlottesville, Virginia during 2006–2009, and in 2007 he was a co-supervisor in the University of Virginia Law Extramural (Moot Court) Advocacy Team. Since his promotion to lieutenant colonel, he continues to teach trial advocacy and criminal law at TJAGLCS as a reserve officer. Coombs is also an adjunct law professor of criminal procedure and trial advocacy at the Roger Williams University School of Law in Bristol, Rhode Island.

From 2003 to 2005, he served as one of four defense counsel in the United States v. Sergeant Hasan Akbar case, a matter which received wide coverage.

In 2009, Coombs left active duty service and began a private practice specializing in defending members of the United States Army. From 2010–2013, he represented U.S. Army Private First Class Chelsea Manning, who was convicted of improper release of classified information to WikiLeaks.