An Alexandria judge set a $50,000 bond for accused sniper-slayer Phillip Joseph Steeves at an impromptu court hearing yesterday, less than four hours after another judge had denied bond for the 21-year-old Marine corporal as premature.

Steeves, charged with murder in the shooting death of 24-year-old Mary Ann Montecalvo in Alexandria early Wednesday and a suspect in two other shooting incidents that day, had been formally arraigned before General District Court Judge Daniel F. O'Flaherty yesterday morning.

O'Flaherty denied a defense request that bond be set for Steeves, who has been held in the Alexandria City Jail since early Thursday. O'Flaherty said assistant prosecutor Randy Sengel's request that Steeves undergo a psychiatric evaluation, defense attorney John E. Kilcarr's subsequent objection, and the lack of a firm preliminary hearing date made bond premature. o

O'Flaherty set a tentative preliminary hearing date on May 29 and said he will decide at a hearing on Tuesday whether Steeves will undergo psychiatric tests.

But Kilcarr appeared later before a different Alexandria judge to ask that he be allowed to withdraw as Steeves' lawyer, according to Sengel. Judge Robert Colby accepted Kilcarr's request, appointed former federal prosecutor Alfred D. Swesrsky to defend Steeves, and set bond at $50,000, Sengel said.

Asked if he thought $50,000 bond was high enough, deputy prosecutor Richard Mendelson said: "If (Steeves) doesn't get out of jail, it's adequate. . . . From our position, we would have preferred to see no bond set."

Steeves, who surrendered to Maryland State Police Wednesday evening at a Landover Hills service station, sat downcast yesterday in loose fitting, blue prison clothes. He was not required to speak during his arraignment.

Kilcarr, who could not be reached for comment regarding his withdrawal from the case, earlier had waived a reading of the arrest warrant and requested a preliminary hearing date "as soon as possible. It is our intention to plead innocent in this case," he said.

But Sengel asked that Steeves be evaluated by a psychiatrist based "on his behavior at the time of his arrest." Neither Sengel or Mendelson elaborated on the remark in court and both declined to elaborate later.

Kilcarr had objected, saying an evaluation "at this time would have no relevance."

Maryland State Police said separately they will turn over results of their investigation of the two other shooting incidents in which Steeves is a suspect to a state's attorney in Prince George's County. The prosecutor will decide whether charges will be filed in connection with gunshots fired at a car driven by Donald Gee of Stafford County, Va., as he drove on I-295 early Wednesday. Gee escaped injury.

Before a decision is made on charges in the shooting of Marc Gerald Muntz, 28, on the Woodrow Wilson Bridge, authorities must determine precisely where the shooting occurred. Parts of the bridge lie within the boundaries of Maryland, the District of Columbia, and Virginia, Mendelson said.