SCRANTON, PA., FEB. 7 -- A former top aide to Attorney General Dick Thornburgh was convicted today of using cocaine and lying about it when applying for a security clearance.

Henry G. Barr, 47, is the highest-ranking present or former federal official ever convicted of drug charges, Assistant U.S. Attorney Gordon Zubrod said. The verdict sends a message "that those who are charged with enforcing the law ought not violate it. They ought to be prosecuted," Zubrod said.

Barr, who worked at the Justice Department from September 1988 to May 1989, faces up to 12 years in prison and fines of $510,000. He revealed no emotion when the verdict was read.

U.S. District Judge Edwin Kosik said he would schedule sentencing later.

Barr was convicted of conspiracy to possess cocaine, cocaine possession and two counts of making false statements to the government.

His attorney, Charles Scarlata, promised an appeal.

Barr's case was part of a nearly two-year investigation, which Zubrod said was continuing, of white-collar professionals in the Harrisburg area.

The government's main witness in Barr's case, former state prosecutor Richard Guida, pleaded guilty last year to one count of cocaine distribution.

Another former state prosecutor, W. Michael Trant, pleaded guilty to one count of cocaine possession. He did not testify against Barr.

A doctor, a stockbroker and an investment banker also have been charged in the investigation.

Thornburgh testified Tuesday about why Barr was given access to classified documents before a full background investigation was conducted.

Thornburgh said the move was not unusual since Barr indicated he had not used drugs or had not had other problems that would have made him unsuited for such access.

Barr first worked for Thornburgh when Thornburgh was U.S. attorney in Pittsburgh. When Thornburgh later served as Pennsylvania's governor, Barr became general counsel.