A Montgomery County judge will decide today whether Michael Schoenfeld, 17, caused the deaths last summer of three people in a collision on East West Highway, but yesterday the judge acquitted him of three of the four traffic charges in the case.

District Court Judge Eric M. Johnson ruled at the close of the county's case against the youth that prosecutors had left crucial information--the speed at which Schoenfeld was allegedly driving--out of charging documents for two of the counts and made other errors in the third.

Schoenfeld is still facing three counts of vehicular manslaughter and one count of reckless driving.

Johnson said that he will announce his verdict after closing arguments today. Because Schoenfeld is being tried as a juvenile, a judge rather than a jury renders the verdict.

Montgomery State's Attorney Douglas F. Gansler said he disagreed with the judge's acquittals on the speeding citations but said convictions would have resulted in only fines and were not critical to the case. He said the judge can still consider testimony that tire markings showed Schoenfeld's car was traveling at least 68 mph before impact.

"The vehicular manslaughter charges are the most important," Gansler said. "Those are the charges that account for the deaths. Those are the criminal charges."

Schoenfeld, who was driving his parents' Subaru Outback station wagon, is accused of showing "gross negligence" by speeding and swerving the car on a winding, downhill stretch between Wisconsin and Connecticut avenues.

Two teenagers who were in Schoenfeld's car last July 14 have testified that they and others were screaming for Schoenfeld to slow down before he apparently lost control of the vehicle, which spun across the center line and slid into oncoming traffic.

Matthew Waymon and Irn Williams, both 16 and both passengers in Schoenfeld's car, died in the collision, as did John Francis Wert, 40, of Potomac, who was driving a pickup truck hit by the Subaru.

Johnson acquitted Schoenfeld of the three traffic counts after his attorney, David Driscoll, argued that prosecutors had erred by leaving out of the charges the speed Schoenfeld allegedly was driving. Schoenfeld had been charged with driving at a speed greater than reasonable and failing to control speed to avoid a collision. Maryland law requires that the excessive speed be noted in the charging documents.

In the third citation, for excessive speed, the charging document stated that Schoenfeld drove "68 mph in a posted 30 mph zone." However, a police officer and a state highway official testified that, while the speed limit on the stretch of East West Highway where the collision occurred is 30 miles an hour, there is no speed limit sign posted in the area.

Assistant State's Attorney Marc Hall argued that drivers are supposed to assume that such a residential area near Bethesda's downtown business district would have a 25 mph or 30 mph limit. Testimony showed that less than one-half mile from the collision, Schoenfeld had passed a 25 mph speed limit sign on Montgomery Avenue when he and five teenage passengers set out for home from summer school classes at Bethesda-Chevy Chase High School.

On the final day of testimony in the case, the courtroom was again charged with emotion.

Schoenfeld cried at the defense table, wiping his eyes with a tissue, as an assistant medical examiner listed in detail the massive fatal injuries--numerous broken bones, torn arteries and brain injuries--that his two friends and Wert suffered in the collision.

Waymon's parents and Wert's wife, Mary, weren't in the courtroom for the graphic testimony. Williams's mother ran from the courtroom after the pathologist listed her son's injuries. Her sobbing could be heard beyond the courtroom doors.

Schoenfeld's mother, Lucy Schoenfeld, the only defense witness, choked up on the stand when she told how she let her son borrow her Subaru with the understanding that he would drive only himself and Waymon to summer school and then to the mall.

Asked whether she would have permitted him to drive five other teenagers after having his driver's license two weeks, Lucy Schoenfeld's voice turned shaky. "No, no, absolutely not," she said. "He was a new driver, and kids fool around in cars. . . . It didn't seem like a safe situation for a new driver."

Schoenfeld's parents turned in their son's Maryland driver's license after the collision, and the teenager has not driven since, Driscoll said later.