Conviction in Insider Trading Case Reversed : Judicial: An appeals court says prosecutors failed to prove Ivan F. Boesky associate John A. Mulheren Jr. had manipulated stock prices.

NEW YORK —  Another major fraud case stemming from the 1980s crusade against insider trading on Wall Street unraveled Wednesday when an appeals court threw out the conviction of stock speculator John A. Mulheren Jr.

Mulheren, who was linked to the mighty Ivan F. Boesky in Wall Street’s go-go years, was convicted of helping Boesky manipulate stock prices in exchange for inside tips.

The decision by a three-member panel of the U.S. 2nd Circuit Court of Appeals in Manhattan is the sixth reversal or partial reversal of a white-collar criminal case brought under former U.S. Atty. Rudolph W. Giuliani.

Giuliani had launched the unprecedented probe of insider trading on Wall Street and was responsible for bringing landmark cases against speculator Boesky, the investment banking firm Drexel Burnham Lambert and its junk bond chief, Michael Milken.

Although his office was able to obtain guilty pleas from those key defendants, most of the cases that have gone to trial have faltered at the appeals level.

Giuliani, who is now in private practice, pointed out that the cases that were reversed were tried after he left office. The reversals were a result of either judicial error or a mistake during the trial, he said.

“It’s silly to hold me responsible for errors made after I left the U.S. Attorney’s Office,” he said.

Mulheren, 42, a flamboyant and successful stock trader who often attended his trial by helicopter and wore tennis clothes in court, was sentenced last November to one year and one day in prison and fined $1.6 million. He was convicted last July of four counts of securities fraud and conspiracy.

He had been free pending the appeal outcome.