When the court bailiff announces "United States versus John Thomas Ambrose" on Monday in a Chicago courtroom, history will be made.
It will be the only time since George Washington swore in the first U.S. Marshals that a deputy has ever been charged with leaking inside information to a criminal organization.
When Chicago Deputy Marshal John Ambrose broke down doors for the Great Lakes fugitive squad, it was seen across the country during a CNN special report.
But it was what Ambrose was doing behind closed doors, away from the cameras, that authorities say makes him a criminal.
According to federal charges that Ambrose will face beginning Monday, he leaked information about mob investigations.
"The breach could have put at risk the life of one of the most important witnesses ever developed in Chicago against the Chicago Outfit. It could have put at risk US Marshals, and family members of that witness," said Robert Grant, FBI agent in charge.
One of the primary duties of the U.S. Marshal service is to protect government witnesses. The ultra secret, cloak and dagger style witness security program, or WITSEC as it's known, has protected 17,000 people since 1970 and officials claim not one has ever been harmed.
Calabrese was a protected witness. Deputy John Ambrose was assigned to protect him.
According to federal records, as a supervisor, Ambrose had access to confidential case information, including details of Calabrese's cooperation, where he would he housed, and when he would be moved.
It was during secretly recorded prison conversations between Chicago mob bosses that federal agents knew there was a leak.
The discussions between Outfit leader Jimmy Marcello and his brother Michael were in code. But on numerous occasions when they talked about "the babysitter," feds say that was their code name for Ambrose who was babysitting Nick Calabrese and allegedly leaking inside information to the mob through an Outfit connected family friend.
"No system is perfect. And much of what we do depends on trust and confidence and honor," said Gary Shapiro, first assistant U.S. attorney.
Federal authorities said they were shaken by what they said they found and Ambrose was called in and question by his superiors on several occasions. He denied having contacts with mob lieutenants John "Pudgy" Matassa and or with "Little Tony" Rizzo who had recently gone missing and has never turned up.
Records reveal Ambrose told investigators several conflicting stories including one that he leaked outfit information to curry favor with Chicago mob boss John "No Nose" DiFronzo but only for the purpose, he said, of helping to locate federal fugitives in the future.
"John Ambrose is not connected to the mob at all...it rests on impressions and opinions of an FBI agent," said Frank Lipuma, Ambrose' lawyer.
Ambrose lives in south suburban Tinley Park. He has never publicly spoken about this case. In a 2005 TV interview, Ambrose did discuss how his father motivates him to be a federal lawman.
"As corny as it may sound, I feel like he's (my dad) nudging me in a direction or opens my eyes to something," said Deputy U.S. Marshal Ambrose.
Ambrose' father, Thomas, was a Chicago police officer, highly decorated and respected until he was snared in the notorious Marquette Ten police corruption scandal in the 1980's.
Another one of the Marquette ten was William Guidie, John Ambrose' family friend, the one to whom he allegedly passed inside information.
Nothing happened as a result of the breach and Calabrese went onto help convict the top bosses.
Federal judge John Grady said that 40-year-old Ambrose isn't charged with being a member of the Outfit, of murdering anybody or being involved in the Family Secrets Trial and that he is concerned about sensationalizing the proceedings.
That said, Judge Grady is allowing some witnesses in the Ambrose trial to testify from behind screens so no one will see their faces.