During a years-long investigation of Willie Cochran, federal agents used warrantless data collection and surveillance tactics more common in investigations of gangs and terrorists, lawyers for the indicted alderman argue in court documents.

In a motion to suppress evidence filed Friday, attorney Thomas Anthony Durkin, who has represented terror suspects detained at Guantanamo Bay, blasted the fashion in which the FBI combed through the 20th Ward alderman’s email, text messages and cell phone records. Investigators even used a “stingray” device to intercept Cochran’s communications early in the “relentless 34-month investigation,” Durkin wrote.

Reached by phone on Friday, Durkin said federal investigators used court orders, rather than warrants, to get Cochran’s information under provisions of the post-9/11 Patriot Act, statutes that weren’t intended for use as tools to ferret out government corruption.

“There’s a case about (the tactics) now before the U.S. Supreme Court that takes on this very issue,” Durkin said.

“They’ve used a very controversial method of obtaining electronic records and digital evidence, and we think it’s a serious 4th Amendment issue,” he added, referring to the constitutional protection against unreasonable searches.

In a 15-count indictment handed up last year, prosecutors alleged Cochran shook down a 20th Ward business owner and a developer for cash, and raided an account he’d set up to receive donations for needy youngsters and seniors in his South Side ward. In fact, prosecutors said, bank records show Cochran spent thousands of dollars from the charitable account at casinos and even paid off his daughter’s college tuition.

Durkin declined to comment on the numerous withdrawals and expenditures from the account. Another motion, seeking to have Cochran face the charges of bribery and extortion separately from fraud counts, explains away the spending as “sloppy bookkeeping practices,” and notes that Cochran occasionally put his own money into the account.

A copy of a search warrant attached to the motion lays out in greater detail what Cochran spent money from the account he set up for his “20th Ward Activities Fund.” Among the purchases from the fund cited in the warrant were: $1,350 during a 2010 home furnishing shopping spree at Z Gallerie; pricey tires and a fog lamp for a Mercedes; Rihanna and Usher CDs; a “compact juice fountain” and other items from Crate & Barrel; and an iPad. He also withdrew more than $25,000 from ATMs near casinos in northwest Indiana.

The purchases seem at odds with statements in a letter included with the warrant, in which Cochran solicited donations for a back-to-school picnic where 20th Ward children would be given school supplies and winter coats. People who worked for Cochran told investigators that the alderman did indeed host that picnic, as well as Valentine’s Day dances for seniors.

But Cochran also donated to causes closer to home, according to the warrant. In August 20111, a $5,000 check payable to Eastern Illinois University was drawn on the account. In the memo line of the check, Cochran wrote “Scholarship Award,” and EIU records showed the check went to pay Cochran’s daughter’s tuition. In all, Cochran paid $13,000 to Eastern Illinois, the warrant states.