He was acquitted of two charges of lying to federal agents, and sentencing was set for Sept 9. Ambrose, a veteran fugitive hunter with a sterling record until now, is the only person in the 39-year history of the ultrasecret Witness Security Program to deliberately violate its security safeguards.

The program was established to protect witnesses against mobsters and terrorists who would want to silence them with threats or violence, and Gary S Shapiro, first assistant US attorney said the government's ability to get such witnesses to testify depends on their feeling safe from retaliation.

Defence attorney Francis C. Lipuma argued Ambrose was an innocent man who may have 'shot his mouth off' in boasting about his job to a family friend but never betrayed his oath as a lawman. Prosecutors say the person Ambrose told was a former police officer with known mob ties.

Mr Lipuma argued Ambrose was an innocent man who may have 'shot his mouth off' in boasting about his job to a family friend but never betrayed his oath as a lawman. Prosecutors said the person Ambrose told had known mob ties and the secrets made their way to a reputed mob boss.

The protected witness whom the leak involved, Nicholas Calabrese, was the only so-called made member of the Chicago Outfit, as this city's organized crime family calls itself, to switch sides and tell what he knew about mob murders, prosecutors said. Calabrese admitted to taking part in 14 murders himself.

Ambrose was twice assigned to guard Calabrese at a so-called safe site. His testimony in the government's landmark Operation Family Secrets investigation that ultimately sent three mob bosses to prison for life.

Prosecutors have not alleged that Ambrose endangered Calabrese's life but said passing the information effectively delivered it to the mob. -- AP