KANSAS CITY, Mo. (AP) – An appeals court on Friday overturned convictions against two former Westar Energy Corp. executives accused of “looting” the Topeka-based utility and said the most serious charges can’t be retried.

The 10th U.S. Circuit Court of Appeals, based in Denver, said the prosecution’s case against former Chief Executive David Wittig and former Chief Strategy Officer Douglas Lake “hung by a thin legal thread,” based on claims that the men tried to hide their personal use of corporate aircraft from securities officials.

Those claims led jurors in September 2005 to convict Wittig on 39 counts of conspiracy, wire fraud, money laundering and circumventing of internal controls, and to convict Lake on 30 counts.

Wittig was sentenced in April 2006 to 18 years in prison. Lake was sentenced to 15 years.

But the three-judge panel said prosecutors didn’t provide evidence that Wittig and Lake failed to comply with Securities and Exchange Commission regulations on reporting that personal use, and the jury wasn’t told what the SEC required.

Without that evidence, the court said, Wittig and Lake aren’t guilty of wire fraud and can’t be retried on those counts because doing so would expose them to unconstitutional “double jeopardy.”

In addition, the panel threw out the money laundering counts, which were based on the wire fraud, and said those too can’t be retried.

The court sent back the remaining conspiracy and circumvention counts for trial. A 40th count, ordering the men to forfeit millions of dollars in cash and stocks tied to the alleged crimes ,also was sent back to court.

The decision was a blow to federal prosecutors, who have now failed twice to convict Wittig and Lake. Their first trial ended in a mistrial in December 2004 after jurors were unable to reach a decision on more than half of the counts.

A spokesman for U.S. Attorney Eric Melgren said Melgren’s office was reviewing the decision and had no comment.

Jeff Morris, one of Wittig’s defense attorneys, said he was elated by the decision.

“We’re, of course, obviously pleased with the opinion from the 10th circuit and we will now move forward in litigating what remains of the case,” Morris said, calling the decision “a substantial victory.”

The decision also could help Wittig in his attempt to get out of prison, where he has been since January 2006, when U.S. District Judge Julie Robinson determined he had violated the terms of his release while appealing his conviction in a separate, unconnected bank fraud case.

The 10th Circuit has ordered Robinson to resentence Wittig in that case and said the sentence should be no more than six months. Robinson earlier refused to allow him out because of his convictions in the looting case.

An attorney for Lake, who had remained free on appeal, didn’t immediately return a phone call for comment.

During the two previous trials, prosecutors accused Wittig and Lake of engineering a number of schemes to pull additional compensation and benefits from Westar and then hiding them from company and federal officials.

Among the schemes was a plan to spin off the utility’s unregulated businesses as a separate company, leaving the majority of the debt with Westar, which would then merge with a New Mexico utility. The merger would have generated millions of dollars in payments for the two and put them into control of the spun-off company.

Prosecutors also claimed the men arranged to get extra payments for moving to Topeka and persuaded Westar to invest in companies in which they or their families had vested interests.

But the appeals court said that while prosecutors discussed a number of schemes, the fraud and money laundering charges were based on the use of personal aircraft.

During the trial, prosecutors said the men were guilty of not disclosing that they received more than $1 million in benefits from using corporate aircraft for vacations and other personal use.

The judges said the SEC, however, requires companies to report only the additional cost a company incurs when its executives use aircraft for personal reasons and only if it exceeds a certain amount. No evidence was introduced during trial that there was extra expense to Westar or whether it surpassed the government’s threshold.

“The jury could not possibly determine that the reports, which disclosed no personal travel by the defendants, were false,” the court wrote.

However, the appeals court refused to replace Robinson with a new judge – something defense attorneys have long demanded.

“Certainly the defendants disagreed with a number of her rulings, and we have held that several of the defendants’ contentions were correct,” the court wrote. “But those rulings did not display a disqualifying basis.”