District Judge Barton Voigt told Aaron McKinney's lawyers that he is not sure such a defense is allowed under Wyoming law and criticized the defense for invoking it without consulting him first.

``I am concerned about this and where it is going,'' Voigt said outside the presence of the jury. ``We do not have a gay panic defense. I don't know if I'm going to allow it.''

McKinney is charged with murder in the beating death of the gay University of Wyoming student.

The ``gay panic'' or ``homosexual panic'' defense is built on a theory that a person with latent homosexual tendencies will have an uncontrollable, violent reaction when propositioned by a homosexual.

McKinney's lawyers have argued that McKinney snapped during a drunken, drug-induced rage after a sexual advance by Shepard triggered memories of a childhood homosexual assault. The lawyers are trying to save McKinney's life by convincing the jury he is guilty only of manslaughter.

Voigt said the closest defense he could find in Wyoming law is the ``battered woman'' defense, for those who kill a spouse in self-defense.

Defense attorney Dion Custis denied he was using a ``gay panic'' defense. But he said: ``The fact that Matthew Shepard made a sexual advance has a relevance in this case. It's something Aaron McKinney responded to.'' He added that Shepard's behavior helps explain McKinney's state of mind, ``which is a defense.''

The judge ordered Custis to provide a legal basis for his arguments and said he would make a decision later.

McKinney's accomplice, Russell Henderson, pleaded guilty to kidnapping and felony murder in April and received two life sentences.

Gay rights activists praised the judge, saying it is wrong to try to blame Shepard for McKinney's actions.

``The only person at risk here was Matthew Shepard,'' said Wayne Besen, spokesman for the Human Rights Campaign, a gay lobbying group in Washington. ``If Aaron McKinney felt threatened, all he had to do was walk away.''

Although no state has adopted a gay panic defense, it has been used by defense attorneys in some cases involving gay victims.

Experts warned that employing the defense is perilous since it can amount to blaming the victim. Brian Levin, director of the California-based Center on Hate and Extremism, also said the strategy hasn't worked recently because Americans have become more tolerant of homosexuals.

``I feel we've turned a very big corner in that nearly everyone agrees that violence against them is completely wrong,'' he said. ``I don't think you had the same type of atmosphere 20 or 30 years ago.''