The trial of four men accused of killing Navajo tribal police officers Andy Begay and Roy Lee Stanley is threatening to turn into an anthropology course.

When it begins Monday, defense lawyers hope to present testimony about traditional Navajo religious ceremonies and their fear of the dead. It may even explore the reason Navajos look down when speakingThey will develop an alibi that the accused men were at a religious ceremony near the time of the killings. And they may try to blame the killings on non-Navajos.

The 12 jurors and two alternates were sworn in Friday afternoon, and U.S. District Judge J. Thomas Greene set opening arguments for 10 a.m. Monday. The trial had been scheduled to begin Friday, but jury selection took longer than expected and some expert witnesses were delayed in Arizona.

In a hearing late Friday to iron out potential last-minute glitches, defense lawyers wanted to present evidence on cultural matters. But government lawyers opposed the move, saying the court should rely on such factors as statements of witnesses.

Defense lawyer Walter Bugden said that the jury should at least hear about cultural differences, "when four Navajo boys are on trial by a white jury."

The slain officers were discovered Dec. 5, 1987, in the back of a burned-out police van on the Navajo Indian Reservation near Monument Valley, San Juan County. They had been shot and burned.

Prosecutors contend Stanley was moved from one police truck to the other after he was shot.

Defense lawyers want to introduce expert testimony that traditional Navajos won't touch a dead or dying person because of the dread of horrible things that will happen afterward. In fact, they said, Navajos will abandon a house or car associated with someone who has died.

Defense lawyer Robert VanSciver said the Monument Valley area of San Juan County, where the killings happened and where the defendants live, is the most conservative or traditional part of the Navajo reservation.

People there are taught it's profoundly wrong to touch a dead body.

"If there's an accident on the reservation, there's a high probability that nobody will help," he said."It's almost an intuitive reaction."

"If a person was inclined to shoot another person, I'm not certain how relevant the custom would be," Greene said.

Seen from another angle, Bugden said, that's exactly the point. If Navajos believed so strongly that they shouldn't touch the bodies, then evidence of this belief "goes to the very identities of the perpetrators . . . that these very boys as traditional Navajos . . . would do anything they could to avoid doing that."

Bugden said that in the case of an accident, "the sheriff's office would frequently be contacted, rather than have the Navajo police touch them."

Assistant U.S. Attorney Stewart Walz said FBI agent James Downey was present during a bicycling accident on the reservation, in which the victim was bleeding badly, and a Navajo helped.

VanSciver said an important part of the defense will be that defendants "were in a (religious) ceremony at the time of the offense." Or, he later said, maybe not at that exact time; maybe they were asleep in a house next door.

He wants the jury to learn about non-verbal ways of communication among the Navajo.

"It's even impolite to use in the presence of a witness his own name," he said. Also, when witnesses speak, "There won't be eye contact."

VanSciver wants to have an expert talk about such cultural differences, so that jurors won't think a witness is lying if he won't look them in the eyes.

Walz said federal rules don't allow telling jurors how to take the demeanor of witnesses; that's up to the jurors alone, he said.

If the defendants want to contend they are traditional Navajos with traditional beliefs, let them get on the witness stand and say it, he said. If defense lawyers worry about witnesses looking down, they can ask them what they mean by doing that, he said.