Giuliani, a candidate for the Republican presidential nomination, testified about Bernard Kerik, who served as corrections commissioner and police commissioner under Giuliani in New York. The former mayor also backed Kerik for the position of U.S. secretary of homeland security.
The Times said it has obtained a transcript of Giuliani's testimony. He reportedly told the grand jury that he was briefed about Kerik's involvement with Interstate Industrial Corp., which was seeking a city license.
The company paid $165,000 to renovate Kerik's New York apartment. In 2000, city officials did not know of the relationship, but did know that Interstate had hired Kerik's brother.
Kerik pleaded guilty last year to charges involving Interstate.
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