Montgomery County Chief Administrative Judge David L. Cahoon, whose 35 years of public service range over all three branches of county government, has announced to a surprised courthouse that he will retire from the Circuit Court July 31.

"The ship is trim and running well," Cahoon said. "But I've put in 10 years in the administrative operations . . . it's time to step down and consider other opportunities."

Cahoon, 64, who has served as chief Circuit Court judge since 1975, said he had no specific plans except "I don't intend to be idle."

Cahoon is widely credited with streamlining the operations of the courthouse. "He took over a bad ship and stabilized it," according to Clerk of Court Howard Smith.

The judge was responsible for instituting the tape recording of witnesses' testimony and a "one-day jury system" -- Cahoon calls it "treating jurors like human beings" -- that cuts short most prospective jurors' required service.

Yesterday, friends and coworkers described him as a straightforward, wry, conscientious person, a progressive thinker looking for ways to make government work better.

"As long as I've known him," said Alexander J. Greene, former mayor of Rockville and now staff assistant to the county executive, "Dave's been dedicated to government -- concerned with its structure, its role and the proper exercise of its functions."

County Executive Charles W. Gilchrist, a longtime friend, called Cahoon "an innovator within the courts and a skilled advocate for the court system."

Cahoon, a graduate of Georgetown University Law Center, served as counsel for the towns of Garrett Park and Brookville and the city of Rockville, then, in 1958, was elected to the Montgomery County Council. In those days, he recalled, the council was "both the legislative and executive agency." A Democrat, he was active in the passage of civil rights laws in the county.

He served on the council until 1962, became county attorney in 1967 and was named to the bench by Gov. Marvin Mandel in 1971. As chief judge, Cahoon is responsible for preparing the court's budget, approving routine case assignments and making special assignments, providing technical and personnel services for the courts and hearing pretrial arguments. His yearly salary is $66,000, the same as other Circuit Court judges.