MONTERREY, Mexico » The marines barged in at dawn and grabbed her 27-year-old son, dragging him away with a look of fear frozen on his face, Maria del Socorro Maldonado said. He was rushed out clad only in orange shorts.

"I asked if I could give him some clothes, flip-flops, a shirt and they just took him," she said, still in shock as she recounted the June 28 raid at her home near here.

She has not seen him since. The marines, increasingly used as part of a military saturation of the area to fight drug gangs, say they do not have her son Rene Jasso Maldonado while the local police keep telling the family to check with the marines. Where he is, or even who took him, remains a mystery.

Jasso’s relatives believe he fell under suspicion because he is a taxi driver, many of whom are gang lookouts. But they insist he had no involvement in crime and have filed complaints with every authority they can think of — even sending a letter to the president — as they confront the kind of a bureaucratic black hole that human rights activists and international organizations contend is all too common.

The widespread use of the military to back up the local police, who often lack the capability or willingness to take on drug organizations, has led to the capture or killing of dozens of people suspected of participation in organized crime. But cases like that of the Jasso Maldonados, with their mix of suspicion, fear and unanswered questions, show the darker side of the strategy, human rights groups say.

Like the police, the military has been accused of acting with impunity, getting rebukes by the United States, international organizations and human rights advocates. Last year, the United States withheld part of its drug enforcement aid out of concerns over police and military abuse, and in April, a United Nations panel urged Mexico to consider withdrawing its use of the military because of complaints about "involuntary disappearances."

The most recent, and possibly most far-reaching, effort to bring accountability to the military, however, has come out of Mexico itself: a supreme court decision last month that may help lift the lid on the thousands of complaints against the military about disappearances, torture and other abuse.

The court, concurring with a ruling by an international court, said rights cases against the military belonged in civilian courts, not in military tribunals where wrongdoers are rarely punished.

The decision raises the prospect of more transparent civilian investigations into the cases, said Nik Steinberg, a researcher with Human Rights Watch, which has been tracking military cases. But military leaders declared afterward they could not operate without some protection from prosecution, and several lawmakers came out to support them.

The ruling stemmed from a 1974 case, pressed for years in national and international courts by the family of Rosendo Radilla Pacheco, an advocate for health and education in a poor area of the southern state of Guerrero, who disappeared after being stopped at a military checkpoint. At the time, Mexico and other Latin American countries were taking a hard line on perceived leftist agitators.

Typically, civilian authorities defer to the military, a powerful institution with the trust and a mandate from President Felipe Calderon to take on the cartels while the police and other law enforcement institutions are built up.

Up to 45,000 troops have been sent to several states to assist, and sometimes take over for, civilian forces — the most boots on the ground in highly populated areas since the Mexican Revolution, said David Shirk, principal investigator for the Justice in Mexico project at the University of San Diego’s Trans-Border Institute.

"The Mexican military has experienced a dramatic and sustained mission creep from the 1940s to the present," Shirk said. "Its role has shifted from eradicating drug crops in remote rural areas to its current urban deployments to restore order and reclaim lost spaces in Mexico’s largest cities."

But as complaints of human rights abuses have risen, Mexico has grappled with how, or even whether, to police the military.

The National Human Rights Commission said it has logged more than 5,000 complaints of abuse at the hands of the military, chiefly the army. In addition, it has said, more than 5,300 people have been missing since Calderon began his offensive against organized crime in 2006.

Under international pressure to curb the use of torture and arbitrary detentions, Calderon proposed to Congress late last year that allegations of rape, kidnapping and torture against the military be heard in civilian courts. Murder was left off the list, to the dismay of human rights advocates, and the bill has not advanced.

The State Department last year withheld part its counternarcotics military aid over human rights concerns. The money, $26 million under the $1.4 billion Merida Initiative, still has not been delivered, though the court’s decision on July 12could help persuade lawmakers to release it, State Department officials said.

But several analysts questioned whether the civilian justice system was prepared to take on such cases.

"Mexico’s civilian courts have proved woefully ineffective," Shirk said. "If military human rights violators find the same degree of impunity we see for other criminal actors, then their victims will have little justice and this decision will have little real meaning."

Military leaders have long expressed skepticism over the complaints, arguing that most are unfounded or the work of cartels manipulating human rights and international organizations with false accusations to tarnish their name.

Just last week, the secretary of the navy, Adm. Mariano Francisco Saynez, said as much at a graduation ceremony for cadets.

"By using the banner of human rights, they try to damage the image of our institutions with the malevolent goal of obstructing their participation in the fight against them and having an open field for their evil doing," Saynez said.

Still, he added, the marines "do not tolerate or protect those who by mistake or lack of professionalism violate human rights." Both the navy and the army say they now incorporate human rights awareness into their training.

The use of the military against the drug organizations remains highly popular in Mexico, though a number of cases here in Monterrey and surrounding Nuevo Leon State have raised alarms. Several people later acknowledged by authorities to have been innocent victims have been wounded or killed at checkpoints or in military operations, in some cases with soldiers accused of manipulating crime scenes to cover their tracks.

But among the more worrisome cases, human rights advocates said, are the disappearance of people, typically young men, last seen in the custody of or near military units. In Tamaulipas State, which borders Nuevo Leon, Amnesty International in June said witnesses reported four men being picked up by marines and not heard from again, with the marines denying any involvement.

"Whether they were suspects or taken by mistake is often hard to know because nobody claims to have answers," said Sister Consuelo Morales Elizondo, director of Citizens in Support of Human Rights in Monterrey.

Confusing matters further, cartel hit men often disguise themselves as police or soldiers, using fake equipment and sometimes authentic gear stolen or procured from allies in the agencies. That has allowed the authorities to dismiss many disappearances as the work of "clones."

The marines told Jasso’s family that it had not been operating in the area and suggested it might have been a gang in military disguise.

But his brother, Oziel, doubted that. He works as a toll taker on a federal highway and said he sees military convoys all the time, readily recognizing their insignia and manner.

One officer during the raid kept accusing him of being a "hawk," slang for a cartel lookout, before deciding he was not involved and moving on to find his brother.

"If it was a cartel, I would not be sitting here talking to you," he said. "They would have wiped out the witnesses."

A few days after the raid, Rene Jasso Maldonado’s close friend and fellow taxi driver, Jesus Llano Munoz, 22, was detained at a military checkpoint, according to witnesses, and he has not been heard from since.

Llano’s family members said they believed rival drivers spread false information about Jasso and Llano among the marines and soldiers in an effort to eliminate competition.

"All we want to know is where he is," Oziel Jasso Maldonado said.

© 2011 The New York Times Company