Leading up to November's veto-override votes, lawmakers were visited by Marvin Reeves and James Kluppelberg, who, thanks in part to jailhouse informants, spent a combined 43 years in prison for separate murders of which they were later cleared. The law's sponsors believe vetting testimony before trial will prevent future mistakes.

"Once the jury hears it, true or not, it's going to influence a decision one way or another," said House Deputy Majority Leader Arthur Turner, a Chicago Democrat who sponsored the measure with Sen. Michael Hastings, a Democrat from Tinley Park.

"If it's not credible information, or the judge deems it something that should not be used, or (there is) some sort of conflict or questionable interest by the jailhouse informant, then we don't want the jury to be tainted," Turner said.

The law has been on the books since 2003, but it applied only to cases involving the death penalty — a reform put in place after former Gov. George Ryan declared a moratorium on capital punishment in 2000, calling the system "haunted by the demon of error."

Lawmakers, preoccupied with a process that since reinstatement in 1977 had executed 12 but seen 13 released because of wrongful convictions, didn't consider a test for penalties other than death. When executions were abolished in 2011, the law became moot.