Arlington prosecutors, saying they did not have enough evidence, yesterday dropped a murder charge against a Silver Spring man who had been in jail since April 19 as a suspect in the slaying of a motorist.

In a hearing that lasted less than five minutes before General District Judge Eleanor S. Dobson, Assistant Commonwealth's Attorney Liam O'Grady moved to drop the charge of first-degree murder against Deonicio N. Vivar, 23, of 8670 Piney Branch Rd.

Vivar was charged in the shooting death last July 27 of 39-year-old John P. Green, of 1501 N. Pierce St., Arlington. Green was shot in the head and chest while driving his red pickup truck along North 10th Street about 11 p.m.

Police said at the time that a traffic altercation may have prompted the shooting.

"I think a charge was properly placed against Mr. Vivar," O'Grady said in court. "But we do not have proof beyond a reasonable doubt at this time."

"My client has proclaimed his innocence from the start. The commonwealth has never had enough evidence to convict him," said Richard J. McCue, Vivar's court-appointed attorney, after the hearing.

Vivar had been charged in the District of Columbia with second-degree murder while armed in connection with the shooting of two men outside an Adams-Morgan restaurant on Dec. 15.

In a D.C. Superior Court hearing Dec. 24, that charge was reduced to accessory after the fact of second-degree murder while armed, and Vivar was released on his own recognizance.

When Vivar, an employe for a Germantown construction company, was arrested April 19, police said the strongest link to the Arlington shooting was a .32-caliber handgun seized by D.C. police after the December incident.

"The gun used in the Arlington case was also used in the D.C. double-homicide case. It's positively the same gun," Arlington Police Sgt. Frank Hawkins said shortly after Vivar's arrest.

Arlington Commonwealth's Attorney Henry E. Hudson said yesterday that the gun "is a significant factor but, in the context of other evidence, we don't feel it would have been sufficient" to bring the case to trial.

Vivar's preliminary hearing, originally scheduled for May 24, was postponed three times at the request of prosecutors. "There were a number of investigative leads in the preceeding weeks that failed to bear fruit," Hudson said. "We were hopeful up until the very last moment that additional evidence would materialize."

He said Green's shooting is still under active investigation, and noted that Vivar could be charged again if more evidence is found.