Despite being highly critical of the prosecution, a Southern District judge on Wednesday refused to suppress more than 18,000 wiretapped conversations gathered over 19 months in building an insider trading case against one-time-billionaire Raj Rajaratnam, the head of the Galleon Group.

Even though prosecutors from the Southern District U.S. Attorney’s Office had made a misleading application seeking authorization for the wiretaps by omitting the “heart and soul” of the data already gathered in a prior investigation, Judge Richard J. Holwell concluded that the wiretaps were necessary because without them, Mr. Rajaratnam might have foiled the investigation.