Investigators with the Cook County state’s attorney’s office are sworn police officers who are supposed to help prosecutors with criminal cases, whether that means serving subpoenas, tracking down witnesses or conducting interviews.

But one veteran investigator added something else to his job description: smoking for hours on end inside a Bridgeport cigar shop while on the taxpayers’ clock.

Now he’s out of a job, and reforms are supposedly underway in the 130-person unit that, sources say, long has been known as a place to coast, especially for those with clout.

An investigation by the Better Government Association and FOX Chicago News found Robert L. Thomas – a retired Chicago cop hired by the state’s attorney’s office in 1997 – spent large parts of his days hanging out at Gianni Cigars Etc. at 31st and Canal when he was supposed to be working. (When the shop moved a couple of blocks away this month, he started showing up there, too.)

The BGA and FOX watched on hidden camera over a few weeks as Thomas chatted up patrons and puffed on stogies, sometimes for several hours, while his government-issued sedan was parked outside and his timesheets showed he was supposed to be doing real work.

Just days after the 66-year-old Shorewood resident was confronted on camera and asked why he frequented the shop on duty, Thomas resigned his $78,000-a-year position – although he still, apparently, will be able to collect a public-sector pension through Cook County. He already is collecting a Chicago police pension of around $40,000 a year.

“It’s disappointing,” Jack Garcia, the new chief of the investigations bureau for the state’s attorney’s office, said of the situation. “I immediately opened up an internal investigation. . . . Everybody here has been put on notice that we will do what we’re expected to do at all times.”

The cigar shop has its own intriguing history that raises more questions for Thomas: reputed mob figures visit there, according to sources, and government documents.

For instance, brothers Bruno and Frank “Toots” Caruso – former union officials whom the FBI has identified as members of the Chicago mob – have been seen by authorities at the shop (under a previous name and owner), and the current owner said they still stop by.

Bruno Caruso, however, told the BGA he doesn’t know Thomas and gave up cigars some years back. Frank Caruso couldn’t immediately be reached for comment.

Thomas said he knows who they are, but stays clear. “I just say ‘hi’ when they come in,” he said. “That’s my only involvement.”

Garcia said he’s cracking down on his supervisors so they know where their people are during the day.

So who was Thomas’ direct boss?

Turns out to be a state’s attorney employee named Frank Cupello, who FOX and the BGA profiled some weeks back for allegedly engaging in vote fraud – regularly voting from Elmwood Park even though he lived for decades in Lake County. Cupello has close ties to Elmwood Park Mayor Pete Silvestri, who also is a Cook County commissioner.

Cupello gave Thomas good job performance ratings, marking on one review that Thomas is “exceeding expectations” when it comes to “time and resource utilization,” according to a copy obtained under the Illinois Freedom of Information Act.