Former Prince Georges County executive Jack Johnson(R) walked up to the Federal Courthouse for his plea hearing on May 17, 2011 in Greenbelt, Md. (Mark Gail/THE WASHINGTON POST)

Jack B. Johnson, the former Prince George’s County executive who is the central figure in a sweeping public corruption case, is scheduled to appear in federal court Tuesday for a plea agreement hearing.

The hearing is scheduled for noon at U.S. District Court in Greenbelt, according to the Maryland U.S. Attorney’s Office. Such proceedings typically mean prosecutors and the defendant have reached a deal to plead guilty.

But even when a defendant has signed a plea deal, it is not official until he pleads guilty before a judge.

Johnson, whose two terms as county executive ended in December, pleaded not guilty in March to corruption charges.

This month, his wife, Prince George’s County Council member Leslie Johnson (D-Mitchellville), was expected to enter a guilty plea but the hearing was canceled.

Efforts to reach Jack Johnson’s attorney, Billy Martin, were unsuccessful.

In February, a federal grand jury in Greenbelt indicted Johnson on eight charges, including bribery, witness and evidence tampering and aiding and abetting. Johnson allegedly took more than $200,000 from a developer in exchange for providing him money from a federal housing program called HOME Investment Partnerships.

Jack and Leslie Johnson were arrested in their Mitchellville home in November after a years-long federal investigation.

According to court records, Leslie followed the instructions of her husband and destroyed a $100,000 check from a developer and hid nearly $80,000 in her underwear. Federal agents found the money when they took her into custody.

Leslie Johnson, 59, who was elected to the council Nov. 2., has maintained her seat despite being stripped of some responsibility by the full council. She is charged with conspiracy to commit witness and evidence tampering, a felony. If she is convicted of a felony, she would have to step down from the council, officials have said.

It did not appear that Jack Johnson’s scheduled plea hearing Tuesday is related to developments in his wife’s case, said a federal law enforcement official who is familiar with the investigation and spoke on the condition of anonymity because the case is pending.

The Johnsons are among nine people publicly charged in the far-reaching federal corruption probe. Two county police officers are charged with taking part in a black-market cigarette smuggling scheme, and a third officer is charged with cocaine trafficking.