SCRANTON, PA., FEB. 5 -- Attorney General Dick Thornburgh testified today in the cocaine-conspiracy trial of a former top aide that the aide said during a background check he had never used or distributed illegal drugs.

Thornburgh said the ex-assistant, Henry G. Barr, would not have been hired had he admitted using cocaine.

Thornburgh said Barr was given access to classified documents on the basis of his response to the question about drugs, which he gave during a background investigation when he joined the Justice Department.

The government contends Barr lied during the investigation, and it called several witnesses who testified they used cocaine with Barr on a number of occasions between 1984 and 1989. Barr is charged with one count of cocaine possession, one count of conspiracy to possess cocaine and two counts of making false statements to the federal government about drug use.

Barr became an assistant to Thornburgh in September 1988 and quit in May 1989.

During 30 minutes on the witness stand, Thornburgh was asked by Assistant U.S. Attorney Gordon Zubrod if there was room on his staff for someone who had used cocaine between 1984 and 1988.

"No," Thornburgh said sharply.

Thornburgh spoke highly of Barr, calling him "an excellent lawyer {who} always fulfilled his duties."

Mary Lawton, who supervises the gathering of intelligence for the Justice Department, testified that to her knowledge, Barr never misused classified information to which he had access.