Kansas City, Mo. ? Jurors should have been told about a murder defendant’s mental condition, a state appeals court ruled in ordering a new trial.

Defense attorneys say James W. Boyd III, convicted of first-degree murder in the 1999 stabbing death of a Kansas City teenager, has Asperger’s syndrome, a condition that inhibits social interaction and also impairs motor, visual and spatial skills.

Now 24, Boyd has been serving a sentence of life without parole. He contends he was framed by co-defendants who testified against him.

During his trial, a Clay County judge refused to allow evidence of Asperger’s syndrome.

Usually, evidence of a mental condition is only used to prove such matters as diminished capacity, lesser criminal responsibility or insanity. The trial judge refused to allow testimony about Asperger’s because it did not fit any of those situations.

But the three-judge panel of the Missouri Court of Appeals ruled Tuesday that the evidence should have been allowed because it supported the defense’s argument of innocence.

“The victim’s own mother furnished Mr. Boyd with an alibi,” the court said. “Almost all the evidence against Mr. Boyd came from highly suspect witnesses who had struck plea bargains with the state to avoid much more serious charges in connection with Mr. Weber’s death.”

Defense attorneys had hoped to use Boyd’s condition to explain his odd behavior and show he could have been framed.

Also, two teens testified that Boyd led them into deep woods to see Weber’s body. But Asperger’s would have made that impossible, defense attorneys said.

“The jury lacked a critical piece of the evidence needed for a reliable verdict,” said Boyd’s attorney, Sean O’Brien.

State Atty. Gen. Jay Nixon’s office is reviewing the ruling, a spokesman said.

Two other teens pleaded guilty to lesser charges in Weber’s death. They received probation and testified against Boyd and another co-defendant, Brett Johnson.

Johnson, 23, was convicted of first-degree murder and armed criminal action after two mistrials. He is serving life without parole.