The courts of Montgomery County are filled with complainants seeking back wages from their former employers, but few so unusual as the one filed this week by Joseph E. Baltimore.

Baltimore is a former Montgomery County police officer. He is seeking $75,000 in back wages and damages from a department that suspended him in 1977 for allegedly having sex with a 15-year-old girl. He also is a fugitive, whereabouts, unknown, who has been sought by police since June 1 when he was charged with robbery of two local supermarket managers.

"If ever there was a classic demonstrataion of chutzpah," said one attorney close to the case, "this is it."

The lawsuit was filed on Baltimore's behalf by his lawyer, Courtland K. Townsend, who would not reveal when or how he arranged the legal maneuvering with Baltimore and said yesterday that he did not know the answer to "the question that everybody is asking" -- where is his client?

"We still don't know where he is," sid Cpl. Phil Caswell of the Montgomery County Police Department. "His attorney emerged. Baltimore still hasn't emerged. If he did, we would want to get him."

Law enforcement authorities say Baltimore, 36, was the suspect they were chasing the night of May 31 after a Safeway manager in McLean was robbed of a bagful of money. The suspect in that case was wounded by a security guard, but managed to escape in a car to Bethesda, where he was involved in an accident, but nevertheless managed to evade pursuers.

The next day, Fairfax officials charged Baltimore with the robbery of Safeway manager Donald Oakes, and Montgomery police charged him with the May 10 robbery of a Safeway store in Rockville that was almost identical to the heist in Virginia.

Baltimore last served on the Montgomery gomery police force in February 1977, when he was suspendedf pending the outcome of rape charges involving a 15-year-old girl. He was found innocent of those charges, but then faced dismisssal proceedings by the department, which charged that he had violated regulations by having sex with the girl -- a charge Baltimore has always denied.

The lawsuit claims that Baltimore won the fight to retain his job in 1978 and, although he never rejoined the force, did not submit his resignation until April of this year. The suit fails to specify a time frame during which Baltimore would be due back wages, nor does it specify damages sustained during that time.

Major Thomas McDonald, chief of field services of the Montgomery County Police Department, said his records show that Baltimore filed a letter of resignation in April 1978 -- two years before the date claimed in the lawsuit. Noting that Baltimore's civil action is unrelated to the crimnal charges against him, McDonald said: "We will respond to the lawsuit."

One stumbling block for Baltimore's effort to obtain back pay is that the law permits the defendants -- in this case, Montgomery County -- to demand an oral deposition from him. It would be difficult if not impossible for Baltimore to win the suit without making such a deposition or appearing in court in person, officials say.

Another probable difficulty, attorneys say, is that the presiding judge likely would dismiss the lawsuit becausethe plaintiff was not coming to court with "clean hands."

Baltimore's brother, Philip Baltimore, who lived with Joseph in Silver Spring last year, said the former police officer had been taling about a lawsuit for months before he became a fugitive. Phillip said his brother had felt ever since his first battle with the department that "he didn't get all the money he was due."

"He wouldn't go back to the police force," the brother said. "He felt very hurt that the department wouldn't back him up on this, and he thought they had treated him unfairly. He just didn't want to go back after what they had had done to him."

Philip Baltimore said he didn't know why Joseph had disappeared.

"The only thing I can think of is that he didn't want to go through what he went through before. . . . It left a scar on him."

For the last three years, said Philip, his brother has been earning a living by selling firewood from a farm he owns in Virginia and by managing a horse farm in Upper Marlboro. He said Joseph had no intention of returning to police work and seemed to be pursuing a life in farming.