HUMAN RIGHTS : Wife’s Search Embarrassing for Guatemala : American digs for truth about disappearance of her rebel-commander husband, shining spotlight on country’s human rights record.

They were an unlikely couple: he a Mayan Indian born into abject poverty who became a top guerrilla commander, she a WASPy-looking Harvard law graduate.

The friendship and subsequent marriage of Efrain Bamaca, better known as Comandante Everardo, and Jennifer Harbury, from Austin, Tex., is producing a major embarrassment for the Guatemalan military, so keen to improve its abysmal image as an endemic violator of human rights.

Bamaca disappeared on March 12, 1992, after a battle between his leftist guerrilla faction and the army. The army claimed that he died and was buried, but an exhumation last month of the purported grave failed to produce his body. Where is he?

Harbury is determined to find out and, in the process, expose what she and human rights monitors claim is Guatemala’s continued practice of detaining suspected guerrillas in clandestine jails.

“My life has been dedicated to finding him since he disappeared,” Harbury, 41, said in an interview. “I’m asking the new Guatemalan army to make amends for its past and bring prisoners to court.”

The army denies that it holds any captives secretly.

To press her cause, Harbury staged a six-day fast outside military installations in central Guatemala City. One day last week, a plastic sheet protected her from the steady rain. Behind her flapped a banner with the names of 36 guerrillas Harbury charges are being held incommunicado at military bases.

So far, Harbury has not received help from the government of President Ramiro de Leon Carpio, himself a former human rights ombudsman whose election by Congress three months ago raised hopes that Guatemala’s ignominious history of military abuse might be ending. During 32 years of civil war, a brutal army killed tens of thousands of Mayan peasants, and similar numbers disappeared.

For Harbury, the search has involved the frustration of challenging military and government obstacles and denials. One exhumation last year was abruptly halted by Guatemala’s attorney general. The second, in August, produced the body of a man considerably younger and shorter than Bamaca.

Her own investigations originally led Harbury to conclude that her husband had been captured alive in the battle but had probably been killed later. Then in January of this year, she met “Carlos,” a former member of Bamaca’s group who says he was captured by the army in 1991. Carlos told her he saw Bamaca in March, 1992, after the battle, at a military base at Santa Ana Berlin.

Carlos said the captured guerrillas were part of an experiment, an indoctrination program run by military intelligence to convert them through physical and psychological torture into secret, long-term informants.

At the end of May or in early June last year, according to Carlos, the prisoners were rounded up and told that Bamaca had been shot trying to escape. But in July, Carlos saw Bamaca again at another base in San Juan de Loarca. He was in the infirmary, strapped to a metal table.

“They’d swollen his whole body, and one arm and one leg were bandaged,” Harbury said Carlos told her. He added that Bamaca had obviously been drugged, because he was babbling. But he was alive.

The military denies that it is holding any members of the rebel Guatemalan National Revolutionary Union (URNG), or that clandestine jails exist.

“We do not know if Bamaca is alive or dead,” says spokeswoman Maj. Edith Vargas.

Harbury testified this month before a delegation from the Organization of American States that was in Guatemala to assess the human rights situation. Oscar Lujan Fappiano, the delegation’s Argentine head, told reporters that the OAS believes the army is holding guerrillas illegally and that Bamaca may be one of these.

“The evidence . . . shows that there have been cases of detainees who have not been treated in accordance with the law,” Lujan said.