Retiring 25th Ward Ald. Danny Solis traded official acts for campaign contributions, sexual favors and more, according to reporting by the Chicago Sun-Times, which based its story on an affidavit filed in federal court as part of “an explosive search warrant application.”

The particulars of that document may not be clear to people unfamiliar with federal investigations – so what exactly is it?

“When a federal agency wants to go and search your house or search your offices or whatever it is, a federal agent authors an affidavit,” said criminal defense attorney Gal Pissetzky of the law firm Pissetzky and Berliner. “The affidavit has to lay out information to show a judge … that there’s enough probable cause, enough information in there that a crime may have been committed.”

Patrick Cotter, a former federal prosecutor and a longtime white-collar crime defense attorney at the law firm Greensfelder, said it’s “fairly stunning” the Sun-Times was able to obtain the affidavit. “This is a secret document,” Cotter said. “It would not normally be unsealed unless and until there were a federal prosecution and if it were deemed to be something that the defendant was entitled to see.”

Michael Monico, a former federal prosecutor better known for his work as a criminal defense attorney as a partner at Monico and Spevack, also said it’s almost certainly not the only such affidavit related to the Solis investigation.

“Once you get a search warrant, every month you have to go back to the judge and tell the judge that we have successfully gotten all these phone calls, and you have to convince a judge that either a crime has been committed or will be committed, and for that reason we need to continue this search warrant,” Monico said.

Cotter says the depth and breadth of the investigation into Solis – and the sheer volume of phone calls and recordings involved – is remarkable.

“Twenty-thousand intercepts is a lot of intercepts. We’re now, apparently, starting the fifth year of this investigation, at least,” Cotter said. “It is unusual. It’s not unprecedented, but it’s a very long time to be up on one guy.”

Pissetzky says the thorough nature of the investigation is reflected in the document on which the Sun-Times based its reporting.

“This affidavit is 120 pages long, according to what we know. It’s a very long affidavit. If you look at Burke’s affidavit, it’s much shorter,” Pissetzky said. “I think there’s information here that the government or the agent tried to bombard the judge with to show what he would call probable cause – but it’s a lot of nothing, possibly.”

The three attorneys also say it’s unclear based on what we know whether the investigation turned up evidence that House Speaker Michael Madigan committed any crimes.

“One thing we do know is that Solis was in trouble,” Monico said. “Solis was in such trouble that he agreed to (wear a wire).”

But even though Solis eventually cooperated with the federal investigation, that doesn’t mean he’s immune from future legal trouble.

“Many cooperators, even after their cooperation or indeed as a term of their cooperation right from the beginning, they’re going to be charged with a crime,” Cotter said. “Now whether that’s the deal he cut or not, we don’t know yet. But simply the fact that he’s cooperating does not mean that he gets a ‘get out of jail free’ card.”

Related stories:

Speaker Madigan the Latest Snared in Solis Wiretap

Released Documents Detail What Feds Sought in Burke Raid

Former Federal Prosecutors Expect More Charges in Burke Probe