The undercover D.C. policeman who is the key prosecution witness against a McKinley High School student charged with selling PCP, cocaine and marijuana filed official reports stating that he "attended all classes" at the school on three student holidays.

The officer, James Simpson, a member of the police department's "school squad" who was reponsible for the arrests of seven McKinley students, including two juveniles, on charges of selling drugs on school grounds, filed the reports as part of his assigned duties.

Charges against one of the students, Laruan Queen, 20, were dismissed by the government two weeks ago because of a discrepancy between the approximately 5-foot-10-inch height of the person Simpson said he bought drugs from and that of Queen, who is well over 6 feet.

In addition, defense attorney David Woll told the court a McKinley teacher would testify that Queen was taking a test in her classroom at the time of the alleged drug purchase.

Two other McKinley students indicted on federal charges have pleaded guilty to lesser drug distribution counts, and a third student, Guy Johnson, has been found guilty by a jury of six counts of drug distribution near school grounds.

Simpson, who could not be reached for comment last night, cited two of the reports -- for Nov. 29, the day after Thanksgiving, and Dec. 24 -- as evidence that could corroborate his reports for Oct. 25, the day he testified he purchased PCP and marijuana from a student he later identified as Major H. Unger.

Unger, 19, is charged with six counts of drug distribution under a new federal law that provides for prison terms of up to 30 years for selling drugs within 1,000 feet of a school.

Simpson also filed a report stating that he attended classes on Dec. 23, also a school holiday, and on Jan. 27, a teacher-training day on which students were excused from classes.

U.S. Attorney Joseph E. diGenova singled out Simpson for praise when the indictment of four McKinley students was announced May 6, but his office said he had no comment yesterday.

Police sources said they believed Simpson might have been late in filing his reports, which are supposed to be made daily, and simply filled them in with incorrect dates.

The three days in dispute were days on which officers observed students' activities, but did not make drug purchases.

Assistant U.S. Attorney Zinora Mitchell yesterday told U.S. District Judge Louis F. Oberdorfer, who is presiding at Unger's trial, that the reports were a "matter of credibility." The "officer apparently made a mistake," said Mitchell, playing down their importance.

But Unger's attorney, Thomas Lumbard, said in court that he was "shocked," and that the reports filed by Simpson had demonstrated that the officer "lied before this court."

Lumbard asked that Oberdorfer direct a verdict of acquittal for Unger and refer Simpson's testimony to a grand jury for possible prosecution for perjury, but the judge denied both requests.

Arguments concerning Simpson's testimony were made while the jury of eight women and four men was out of the courtroom, but immediately afterward, McKinley attendance counselor Matthew Goode was called to the stand and testified that there were no classes on Nov. 29, Dec. 23 and 24 and Jan. 27.

He also testified that Simpson, who was registered as a McKinley student, was not counted present in homeroom on Oct. 25, the day of the alleged sale, and on another day on which he said he attended all classes.

The case is expected to go to the jury today.

Staff writer Linda Wheeler contributed to this report.