Lawyers for a hedge fund executive charged in a broad insider-trading investigation Tuesday denied Securities and Exchange Commission charges that he used non-public data on Google, Hilton and other firms to gain an improper edge on other investors.

Galleon Group founder Raj Rajaratnam's lawyers also attacked major aspects of the agency's civil lawsuit, including wiretap evidence and the credibility of a potential star witness for the prosecution.

The SEC last month accused the billionaire Sri Lanka immigrant and others of a scheme that produced more than $33 million in illicit profits via trading on secret details of corporate takeovers and quarterly earnings leaked by company insiders.

Federal prosecutors simultaneously filed criminal charges in the broadest insider-trading case in at least a generation. Although the criminal trial hasn't been scheduled, the SEC's civil trial is tentatively set for August.

In a 32-page reply to the SEC charges, Rajaratnam's lawyers argued that the stock trades in question were based on pre-existing investment strategies that Galleon had developed from its own analysts, Wall Street analyst reports or news stories.

Rajaratnam didn't know insiders had allegedly disclosed secret information, and he didn't pay or give anything for leaked information, the attorneys contended.

The defense team argued that the wiretaps violated Rajaratnam's constitutional rights because such surveillance is allowed only for specific alleged crimes when alternative investigative means "have been tried or appear unlikely to succeed."

But at the time of the wiretaps, the SEC had already questioned Rajaratnam under oath "under the guise of another unrelated hedge fund," defense lawyers wrote. Some of the results of that questioning ultimately became part of the case against Rajaratnam, showing that wiretaps shouldn't have been approved, the lawyers argued.