Could he make up this story? No.
Reference Chicago Sun-Times Thursday August 6 2009 titled Murder Trial has a twist.
Jerome Finnigan ex scum cop of Chicago Police Force is under inditment case number is sealed. He shook down drug dealers among various other crimes. Link to inditment www.usdoj.gov/usao/iln/indict/2007/us_v_finnigan_complaint.pdf or tiny url http://tinyurl.com/lfwebx
Now at a murder trial of Daniel Nevarez attorneys for Mr. Nevarez contended that Finnigan killed Eric Kaminski who Mr. Nevarez is accused of killing.
If you were Mr Nevarez would you turn in a diry scumball like Finnigan? This would surely result in your death. So I think bringing this out in open court is a better way to do it. According to the article Navarez's girlfriend was present at in the house were Kaminsiki was killed and she maybe the reason they are able to bring this out in court as they have this witness.
I believe Mr Nevarez's story. Who would you believe a dirty scum cop or a supposed drug dealer? Hard to tell. But I am going to believe Mr. Nevarez.