DETROIT — Legal experts said Tuesday that the heart of the perjury case against Mayor Kwame Kilpatrick _ steamy text messages that seem to contradict his sworn denials of an affair with an aide _ might be less open-and-shut than many believe.

Kilpatrick's attorneys want to keep the intimate and sexually explicit text messages out of a trial, and at least one outside defense lawyer says the admissibility of such high-tech communications is an unsettled legal question. Even if they are admitted, experts say the defense will exploit any ambiguity in the messages, in the questions the mayor and former Chief of Staff Christine Beatty were asked under oath, and in their answers.

"If the questions were not clear, and that's going to be used to prove the case, then that's another avenue in trying to establish a reasonable doubt," former federal prosecutor Matthew Orwig said Tuesday.

On Tuesday, the usually gregarious Kilpatrick was subdued as he stood mute to eight felony charges of perjury, conspiracy, obstruction of justice and misconduct in office during his arraignment in Detroit. Beatty also stood mute to seven of those charges.

Not guilty pleas were entered for both. They were released on personal bonds and are expected to appear at a June 9 preliminary examination that will determine if they will face trial in Wayne County Circuit Court.

The charges stem from a lawsuit filed by two former police officers who won a jury verdict last year. They said they were fired for investigating claims that the mayor used his security unit to cover up extramarital affairs.

Kilpatrick had said he would challenge the verdict, but prosecutors allege that a multimillion-dollar settlement was reached after the officers' attorney showed the mayor's lawyers references to the text messages, which had been left on Beatty's city-issued pager.

The Detroit Free Press published excerpts of the messages in January, prompting an investigation that led to charges against Kilpatrick and Beatty on Monday.

Kilpatrick's lawyer Dan Webb is a former U.S. attorney known for his three-hour cross-examination of former President Ronald Reagan in the Iran-Contra scandal. Webb won a conviction, later reversed, against Admiral John Poindexter on charges linked to the scandal.

Webb also was the chief defense attorney in the corruption trial of former Illinois Gov. George Ryan, who is now in prison.

Webb says the release of the text messages violates federal law.

"Under the Stored Communications Act they absolutely should not have been produced in civil litigation," Webb said Monday. "Because of that, everyone who sees them is clearly tainted because the initial production was illegal."

Miami criminal defense lawyer Milton Hirsch said Webb's effort to bring the 1986 act into play is a good move.

"He's a very fine lawyer," said Hirsch, who specializes in defending public corruption cases. "There is very little law on this, but I think it's a motion worth filing. It could make good law and could establish an important point."

Kilpatrick and Beatty denied having an intimate relationship when they testified in the police officers' lawsuit.

"Mayor Kilpatrick, during 2002 and 2003, were you romantically involved with Christine Beatty?" asked Mike Stefani, who represented the police officers.

Kilpatrick's response: "No."

Beatty said "no" and rolled her eyes when asked if she and the mayor were "either romantically or intimately involved" during the period covered by the case.

Text messages published by the Free Press told a different story.

"I'm madly in love with you," Kilpatrick wrote on Oct. 3, 2002.

"I hope you feel that way for a long time," Beatty replied. "In case you haven't noticed, I am madly in love with you, too!"

On Oct. 16, 2002, Kilpatrick wrote Beatty: "I've been dreaming all day about having you all to myself for 3 days. Relaxing, laughing, talking, sleeping and making love."

The messages also included dialogue about where to meet and how to conceal their trysts. Hirsch, however, said the messages may not be enough to prove perjury.

"The world is full of people who are in the habit of exchanging salacious phone calls, e-mails and text messages," he said. "It doesn't mean they are having an actual relationship. Did they say (under oath) they didn't have physical sex, or have no personal relationship or interaction, at all?

"If the witnesses testified 'we have nothing but a business relationship, we scarcely even talk about anything besides business matters,' that's a different matter," Hirsch said.

Sex is not the only issue surrounding the text messages. The prosecutor's office filed an investigative report Tuesday that included an excerpt of a text message from Kilpatrick asking members of his staff for help in explaining the departure of former Deputy Chief Gary Brown, one of the former officers who sued.

On June 24, 2003, he wrote: "We must answer the question? Why was Gary Brown fired. It will be asked, I need short, powerful answer ... I just need a good answer. Whatever it might be."

During the whistle-blower suit, Kilpatrick said Brown was "un-appointed."

"He was not fired," he testified.

Perjury, under Michigan law, is defined as "willfully" swearing falsely while under oath and is punishable by up to 15 years in prison.

A 2004 Michigan Supreme Court ruling could help prosecutors' case. Reversing more than 150 years of precedent, the court said prosecutors don't have to prove that a lie was material to a case.

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Associated Press Writers Jeff Karoub and David Eggert contributed to this report.