CHICAGO (CBS) — The alleged ringleader of a group of corrupt Chicago police officers was sentenced to 12 years in prison for ordering a hit on another officer, because he believed the officer was cooperating with a federal investigation of their illegal activities.

Jerome Finnigan, 48, pleaded guilty in April to ordering the hit on a fellow officer and to federal tax charges.

U.S. District Judge Blanche Manning handed down the 12-year sentence at a hearing Thursday afternoon.

Finnigan was part of the now-disbanded Special Operations Section, an elite police unit that allegedly robbed suspected drug dealers and innocent civilians. He led a crew of SOS officers who broke into homes without warrants and conducted illegal traffic stops to commit shakedowns.

Finnigan has admitted a role in five robberies in 2004 and 2005.

Prosecutors said the officers stole at least $600,000 and that Finnigan personally pocketed more than $200,000.

Although Finnigan pleaded guilty to the murder-for-hire plot, he has maintained that he never intended to kill anyone, calling the plot a sham.

Keith Herrera, another officer and co-defendant in the SOS case, wore a wire to record Finnigan discussing his plans to have another officer killed because that officer might cooperate with the federal probe of SOS. The murder was never committed.

Herrera has also pleaded guilty to a civil rights violation count and a tax fraud charge.

Finnigan, Herrera and other officers with the now-disbanded SOS were charged in 2006 with conducting illegal searches and traffic stops of suspected drug dealers and innocent civilians and then robbing them of cash and drugs.

The Chicago Police Department disbanded the unit a year after the officers were charged in the case. Finnigan has since resigned from the force.

At least seven other officers have pleaded guilty to state charges in the investigation into corruption in the SOS unit.

According to prosecutors, the officers plotted to stop mostly Hispanic male motorists without probable cause and write false police reports about the stops. They also stole money from their targets and inventoried only a portion of the cash. They would split the rest among their fellow rogue officers.

When suspected drug dealers objected to the illegal searches, the cops would sometimes handcuff them and ordered them to show the officers where they stored additional cash and narcotics, prosecutors said.

They also illegally searched several homes, stealing cash, drugs and other valuables.

Herrera later cooperated with investigators, secretly wearing a wire and recording Finnigan discussing his alleged murder-for-hire plot.