By MICHAEL TARM, AP Legal Affairs Writer

CHICAGO (AP) — Federal prosecutors deny investigators overstepped legal lines by recruiting a confidential informant from former U.S. Rep. Aaron Schock's staff to help build a corruption case against him, accusing the Republican of seeking "to manufacture claims of governmental misconduct" to escape prosecution.

In the same government court filing, prosecutors also raised the prospect that the former Illinois congressman sought to tamper with a witness and urged the person to change grand jury testimony while the investigation was ongoing.

Schock, 35, resigned in March 2015 amid scrutiny over lavish spending, including to redecorate his Washington office in the style of the TV series "Downton Abbey." His attorneys accused agents of violating Schock's constitutional rights against unreasonable search and seizure by using the staffer-turned-informant, and infringed on other rights by pressing the informant to secretly record Schock and other co-workers.

In a sharply worded response filed just before midnight Tuesday in U.S. District Court in Springfield, prosecutors say investigators spelled out clearly to the informant what the person legally could and couldn't do, including prohibiting the person from initiating discussions about legislative matters.

"Schock futilely attempts to manufacture claims of governmental misconduct during the course of the investigation," the 60-page filing says. It downplays the importance of documents the informant secured, saying investigators relied primarily on other sources to form the core of the case.

Schock has pleaded not guilty to theft of government funds and other crimes included in his 2016 indictment. Mark Hubbard, a spokesman for Schock's legal team, declined direct comment on the new government filing, saying only: "We feel the motions we filed before the court speak for themselves."

The defense filing in March said the informant provided the government with a trove of emails, receipts and other documents, sometimes after rifling through staffers' desks, asserting that some of the material should be regarded as stolen property.

Schock's attorneys also accused the FBI of using the informant to sidestep restrictions on what a federal agent can search and seize. Defense lawyers made clear they would follow up soon with a motion to dismiss the case by citing, among other things, alleged prosecutorial misconduct.

Prosecutors also dispute defense claims that the government has withheld vital evidence as Schock's attorneys prepare for trial, which is scheduled to begin July 10. Prosecutors say that includes wiretap recordings, law enforcement reports and grand jury witness transcripts.

Prosecutors say agents first made contact with the informant in March 2015, just weeks after the investigation started. It said the informant voluntarily offered office documents, then later agreed to wear a wire.

The new court document says the informant was an office manager, but it doesn't name the person.

The filing includes several excerpts of conversations the informant recorded with Schock. One was of Schock discussing the investigation against him, saying the government's "gonna have no basis for questions, so it's gonna turn into some giant fishing expedition."

The alleged witness tampering involves a different person. Prosecutors say the witness, who is not identified in court documents, told them in January 2016 that Schock had been in touch. The witness also believed Schock wanted to talk about the grand jury investigation and agreed to record a conversation with him, the court document says.

Schock "wanted to discuss and attempted to suggest an inaccurate account of one of the specific matters ... charged in the indictment," according to the filings. It didn't elaborate.

While Schock isn't charged with witness tampering, prosecutors say the recorded conversation could be played at his trial.

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