A Montgomery County jury last night acquitted a former county police officer of armed robbery and handgun charges stemming from a holdup at a Rockville Safeway store 4 1/2 years ago.

Joseph Ezekiel Baltimore, 40, still faces three other armed robbery charges in Prince George's and Fairfax counties.

A patrol officer in Montgomery County for seven years, Baltimore disappeared in June 1980 as police searched for him in connection with a series of robberies. Last May, two Montgomery police officers located him living under an assumed name in West Virginia.

The Montgomery Circuit Court jury deliberated for six hours before acquitting Baltimore in the May 10, 1980, Rockville grocery store robbery.

While still a Montgomery County police officer, Baltimore was charged in 1977 with raping a 15-year-old girl. A jury acquitted him, but he was later dismissed from the force after a police trial board hearing. That ruling was overturned by a Circuit Court judge.

Baltimore's attorney argued that the experience killed Baltimore's faith in the justice system, leading to his flight after hearing he was wanted on armed robbery charges.

The verdict came after a three-day trial at which the prosecution presented both witnesses and numerous items of physical evidence and Baltimore's attorneys first promised a series of defense witnesses, but presented none.

Assistant State's Attorney Matthew Campbell called nine witnesses for the prosecution and piled 37 items of evidence on a table in front of the jury.

Then, on Thursday, Baltimore decided not to testify. In closing arguments yesterday, Baltimore's lead attorney, Courtland Townsend Jr., apologized to the jury for not presenting the kind of case he had promised. "But blame that on me," he said. "Don't blame it on the defendant."

Townsend then questioned why Campbell had not presented more evidence. He attacked the credibility of Raymond William Walker, who had picked Baltimore's picture out of an array of seven photos shortly after the holdup at the Safeway store he managed on Nelson Road in Rockville.

In the courtroom, Walker stopped short of identifying Baltimore, saying the defendant had a mustache and heavier jowls than the man whose picture he identified 4 1/2 years earlier.

Townsend also criticized Campbell's efforts to link Baltimore to a shootout and a police chase unconnected to the Rockville robbery, but related to another Safeway holdup on May 30, 1980, in Fairfax. "We've spent three days trying the events of an incident that occurred 20 days later" than the Rockville robbery, he said.

Campbell argued that Baltimore had a criminal career that spanned more than four years and took him from Maryland to Virginia and ultimately to West Virginia, where his assumption of a false identity was evidence of his guilt.