Quietly, and with little fanfare, a lawsuit has been working its way through the federal court here in Chicago which has the potential to shake the Chicago Police Department to its core.

At issue are allegations of a "blue wall" in the department, a code of silence where those who raise their hands to report corruption are ostracized and punished and held out as examples to other officers to keep quiet about what they see.

"I think that the public should be very angry that corruption is allowed to continue, and that officers who want to report it are retaliated against," said police officer Shannon Spalding. "The code of silence is so strong, the fear of what will happen to you is so strong, that nobody wants to come forward."

Spalding and her partner, Daniel Echeverria, were part of a 2012 investigation which led to charges against Sgt. Ronald Watts and police officer Kallatt Mohammed, both of whom were accused of stealing proceeds from drug dealers. In the end, the two were only accused with shaking down a single undercover informant who had been posing as a courier. But Spalding and Echeverria said the investigation was stopped before it snared at least half a dozen more officers.

"At one point, we were actually told the investigation was too big," Spalding said. "There were allegations of other supervisors as well, that we were never allowed to investigate."

But it’s what happened next which led to Spalding and Echeverria’s federal lawsuit. They say their role in the undercover investigation was intentionally leaked within the department, leading to years of ostracism and intimidation at the hands of commanders and fellow officers.

"My life, my safety my freedom was threatened," Spalding told NBC 5 Investigates. "I was subjected to daily harassment."

Now a third officer has come forward and has given a sworn affidavit to say she can corroborate the allegations. Former officer Janet Hanna, a 20 year department veteran, says she witnessed the harassment when the two officers were assigned with her in the fugitive apprehension unit.

"They were given dead end jobs that would lead to no arrests," she said. "I couldn’t continue to see that kind of treatment."

Hanna recalled being approached by her commander at the unit’s Homan Square headquarters, warning her that the two were due to arrive the following day.

"He wanted to inform us that there were two people, two officers coming to the unit, they would be there tomorrow, and that they were supposedly IAD (Internal Affairs Division) rats," Hanna said. "I would be in the sergeant’s office and they would throw that term around all the time."

In addition to the dead end assignments, Hanna said she overheard her bosses instructing other officers in the unit that Spalding and Echeverria were not to be given backup if they called for it.

"Nobody wanted to work with her," Hanna said. "If they were to call for backup, nobody should back her up."

On one occasion, she said she overheard a sergeant warning Spalding about her own safety.

"That she’d better wear her bulletproof vest, and she may go home in a casket, and he didn’t want to call her daughter and say, 'She’s gone,'" Hanna recalled.

Indeed, the lawsuit states that in one meeting, one of their supervisors stated, "God help them if they ever need help on the street. It ain’t coming."

Hanna, who recently retired, said the department has no outlet for reporting the type of wrongdoing she allegedly witnessed.

"You’re supposed to go to your immediate supervisor," she said. "But the supervisors were involved in this as well."

Spalding suggested it’s a system which is designed to urge officers to stay quiet.

"I have had many officers approach me and say, 'We know about corruption. Should we come forward?' and I say, 'It will ruin your life,'" she said. "It’s no secret that if you go against the code of silence, and you report corruption, it will ruin your career."

The city's Department of Law, which is representing the commanders named in the lawsuit, declined comment, citing the pending litigation. Police Supt. Garry McCarthy likewise declined a request for an interview. In a statement, he denied the officers’ allegations.

"Superintendent McCarthy and CPD have zero tolerance for retaliation on whistleblowers, and we strongly support the laws that protect whistleblowers," the statement said. "However, the City believes the claims of these particular plaintiffs are without merit. The City will continue to vigorously litigate this case."