Stuart Stiller, 35, a Washington trial lawyer whose clients included former Nixon White House aide John D. Ehrlichman, was fatally injured Saturday in an automobile accident in Bethesda.

Police said Mr. Stiller lost control the the car he was driving north on Wisconsin Avenue near DeRussey Parkway. The car went off the right side of the road and struck a tree. Police said the accident happened about 9:10 a.m. and that Mr. Stiller died at Suburban Hospital of internal injuries at 3 p.m.

Despite his relative youth, Mr. Stiller had established a considerable reputation at the bar as a trial lawyer and a teacher. He was an adjunct professor at the law schools of Georgetown and Catholic universities, where he taught evidence, criminal law and procedure and trial practice.

He also was widely known as a teacher of candidates for the bar examinations. He had lectured all over the United States for this purpose.

Mr. Stiller became involved in the Ehrlichman case when it was being appealed to the U.S. Supreme Court. Later, he was Ehrlichman's chief lawyer in the proceedings before Judge John J. Sirica in U.S. District Court here. Sirica freed Ehrlichman after he had served 18 months of the 2-1/2-to-8-year term he received for his part in the Watergate cover-up.

Sirica reduced the sentences of former White House aide H. R. (Bob) Halderman and former attorney general John Mitchell at the same time.

At the time of his death, Mr. Stiller represented Daniel Minchew, a former aide of Sen. Herman Talmadge (D-Ga.). In widely publicized hearings before a Senate committee, Minchew had accused Talmadge of financial irregularities. Minchew pleaded guilty in U.S. District Corut last week to filing false statements with the Senate concerning expenses.

Mr. Stiller was born in Rochester, N.Y. He graduated from Cornell University in 1966 and moved to Washington that year to study law at Georgetown University, where he earned a law degree in 1969.

He joined the Legal Aid Agency, which later became the Public Defender Service of the District of Columbia. The PDS represents indigent persons charged with crimes. Mr. Stiller became chief of its felony division and remained with the service until 1974.

He then went into private practice with Lawrence H. Schwartz and Robert M. Adler. Their firm, now known as Stiller, Adler, Schwartz & Kaswell, specializes in civil and criminal trial work, including tax cases.

Mr. Stiller, who lived in Washington, is survived by his mother, Mrs. Michael Stiller, of Rochester, and a brother, Frank of Erie, Pa. CAPTION: Picture, STUART STILLER