A Los Angeles man was indicted by a federal grand jury Wednesday for hacking into computer systems so he could rig promotional radio contests and compromise law enforcement investigations.

Kevin L. Poulsen, 27, also was charged with wiretapping and obstructing justice. Through the use of computers, Poulsen and two other men rigged promotional contests on three radio stations and fraudulently won two Porsche automobiles, $22,000 in cash and two trips to Hawaii, according to the indictment prepared by Asst. U.S. Attorney David J. Schindler.

Poulsen faces a maximum of 100 years in prison and $4.75 million in fines.

Poulsen's two co-conspirators, Ronald M. Austin, 29, and Justin T. Petersen, 32, who were about to be indicted, pleaded guilty Wednesday to several charges, including computer fraud, for their roles in the scheme, Schindler said. The prosecutor said Austin and Petersen have agreed to cooperate with the FBI in an ongoing investigation of computer-related crimes.