Former Orange County Sheriff Michael S. Carona lost another round in court Thursday as a federal judge rejected his efforts to obtain investigative files and records in cases that involve three former associates who are expected to be chief prosecution witnesses at his August corruption trial.

U.S. District Judge Andrew J. Guilford also granted the government's request that a magistrate review other subpoenas that have been served or that the defense plans to serve before trial, to ensure that they are proper. The magistrate can order the return of documents that have been improperly provided to the defense.

The decisions follow a series of rulings in the last week by Guilford that support the prosecution's case, including one that will allow jurors to listen to secretly recorded conversations between Carona and former Assistant Sheriff Don Haidl.

One of the subpoenas that Guilford quashed was served on the Securities and Exchange Commission, seeking documents related to the investigation of a company associated with Haidl.

Carona's lawyers also were seeking investigative records from the Orange County district attorney's office related to cases involving Haidl's son, former Assistant Sheriff George Jaramillo and criminal defense attorney Joseph Cavallo. All three men were once part of Carona's inner circle.

Carona resigned in January to face felony charges that he misused his office in a conspiracy to enrich himself and others, including his wife and former mistress. All three have pleaded not guilty. A trial is set for Aug. 26.

christine.hanley@latimes.com