U.S. and Mexico, Amid Drug War, Spurn an Informant The forecast called for record snowstorms, and Luis Octavio López Vega had no heat in his small hide-out. Thieves had run off with the propane tanks on the camper that Mr. López had parked in the shadow of a towering grain elevator, near an abandoned industrial park. Rust had worn through the floor of his pickup truck, which he rarely dared to drive because he has neither a license nor insurance. His colitis was flaring so badly he could barely sit up straight, a consequence of the breakfast burrito and diet soda that had become part of his daily diet. He had not worked in months and was down to his last $250. Going to a shelter might have opened him to questions about his identity that he did not want to answer, and reaching out to his family might have put them at odds with the law. "I cannot go on like this, living day to day and going nowhere," Mr. López, 64, said one night last winter. I feel like I'm running in place. After so many years, it's exhausting. Mr. López, a native of Mexico, said in Spanish that he has lived under the radar in the western United States for more than a decade, camouflaging himself among the waves of immigrants who came across the border around the same time. Like so many of his compatriots, he works an assortment of low-wage jobs available to people without a green card. But while Mr. López blends into that resilient population with his calloused hands and thrift-store wardrobe, his predicament goes far beyond his immigration status. Mr. López played a leading role in what is widely considered the biggest drug-trafficking case in Mexican history. The episode - which inspired the 2000 movie "Traffic" - pitted the Mexican military against the United States Drug Enforcement Administration. Throughout the 1990s, Mr. López worked closely with them both. He served as a senior adviser to the powerful general who was appointed Mexico's drug czar. And he was an informant for the D.E.A. His two worlds collided spectacularly in 1997, when Mexico arrested the general, Jesús Gutiérrez Rebollo, on charges of collaborating with drug traffickers. As Washington tried to make sense of the charges, both governments went looking for Mr. López. Mexico considered him a suspect in the case; the D.E.A. saw him as a potential gold mine of information. The United States found him first. The D.E.A. secretly helped Mr. López and his family escape across the border in exchange for his cooperation with its investigation. Dozens of hours of testimony from Mr. López about links between the military and drug cartels proved to be explosive, setting off a dizzying chain reaction in which Mexico asked the United States for help capturing Mr. López, Washington denied any knowledge of his whereabouts and the D.E.A. abruptly severed its ties with him. The reserved, unpretentious husband and father of three has been a fugitive ever since, on the run from his native country and abandoned by his adopted home. For more than a decade, he has carried information about the inner workings of the drug war that both governments carefully kept secret. The United States continues to feign ignorance about his whereabouts when pressed by Mexican officials, who still ask for assistance to find him, a federal law enforcement official said. The cover-up was initially led by the D.E.A., whose agents did not believe the Mexican authorities had a legitimate case against their informant. Other law enforcement agencies later went along, out of fear that the D.E.A."s relationship with Mr. López might disrupt cooperation between the two countries on more pressing matters. "We couldn't tell Mexico that we were protecting the guy, because that would have affected their cooperation with us on all kinds of other programs," said a former senior D.E.A. official who was involved in the case but was not authorized to speak publicly about a confidential informant. So we cut him loose, and hoped he'd find a way to make it on his own. These are the opaque dynamics that undermine the alliance between the United States and Mexico in the war on drugs, a fight that often feels more like shadow boxing. Though the governments are bound together by geography, neither believes the other can be fully trusted. Mr. López's ordeal - pieced together from classified D.E.A. intelligence reports and interviews with him, his family, friends, and more than a dozen current and former federal law enforcement officials - demonstrates why the mutual distrust is justified. The absence of any facts to either condemn Mr. López or exonerate him of corruption has wrought havoc on the former informant, and his fugitive's existence has been a ball and chain on his family, whom he sees during sporadic rendezvous. They all exhibit symptoms of emotional trauma, bouncing among flashes of rage, long periods of depression, episodes of binge drinking and persistent paranoia. During several long interviews, Mr. López repeatedly said he was not guilty of any wrongdoing. He said he has refused to turn himself in to the Mexican authorities because he believes he will be killed rather than given a fair hearing. But years of living an anonymous, circumscribed life have been nearly as suffocating as a jail cell. He starts most mornings at McDonald's, where breakfast costs less than $2 for seniors and free Wi-Fi allows him to peruse Mexican newspapers on his battered laptop for hours, his mind replaying the life choices that landed him there. I risked my life in Mexico because I believed things could change. Nothing has changed," Mr. López said. I helped the United States because I believed that if all else failed, this government would support me. But I was wrong again. And now, I've lost everything. The Military Steps In These days, Mr. López wonders whether he is losing his mind as well. Last September, he took his troubles to a psychiatrist at a health clinic, telling her how his emotions were running erratically from hot to cold and about his difficulty sleeping. An hour later, he left with a diagnosis of bipolar disorder and a bottle of pills he decided not to take. Sipping Diet Coke in a sunlit hotel room, Mr. López explained that he felt it was riskier to become dependent on medication that could be confiscated if he fell into police custody. More important, he said, the whole diagnosis was based on a lie - one of the many he tells to get by each day. When the doctor asked him what might be causing his stress, he told her that his family had turned against him. "Imagine telling her what is really going on in my life," Mr. López said. Where would I start? That I once helped capture El Güero Palma, and now I'm being treated like a delinquent? Ballads were written in Mexico about the day in 1995 when the authorities took down Héctor Luis Palma Salazar, known as "El Güero," the fearsome kingpin of the Sinaloa cartel. Mr. Palma met his fate on the outskirts of Guadalajara in suburban Zapopan, a nexus for everybody who was anybody in the drug war. Mr. López served nearly two decades in the municipal police department there, most of them as chief. Politically astute and streetwise, he caught the attention of the D.E.A., which developed him as a confidential source during the mid-1990s and valued him for the reliability of his information. Drug violence was raging. When things got too heated, Mr. López sought backup from General Gutiérrez, a powerful ally whose territory spanned five Mexican states. It was part of a secret arrangement, Mr. López said, in which his officers shared information about the cartels with the military and the general provided extra muscle to the Zapopan police. At home, Mr. López's wife and three children lived surrounded by bodyguards and snipers. With her husband often absent, Soledad López had her hands full with the children. Their oldest child, David, got his high school girlfriend pregnant. Luis Octavio failed eighth grade three times. Cecilia, the youngest, did not understand the tumult around her, and Mrs. López worked to protect her from it. By the time Mr. Palma crossed his path, Mr. López had retired to start a private security firm. Mr. Palma had been on his way to a wedding when his private plane crashed in the mountains near Zapopan. Federal police officers who were on the Sinaloa payroll swept him from the scene and hid him in a house belonging to a supervisor. When Mr. López's security guards began receiving reports of suspicious activity there, they alerted him and the military. No one realized they had stumbled across one of the world's most notorious drug traffickers until Mr. López discovered a .45 Colt with the shape of a palm tree, or "palma," encrusted on its handle in diamonds, rubies and sapphires. "It could only belong to one person," Mr. López said. The arrest was hailed on both sides of the border to justify the unprecedented role the Mexican military was beginning to play under President Ernesto Zedillo. The D.E.A. had long been pressuring Mexico to deploy the military against the cartels instead of the federal police, which often worked with traffickers instead of against them. The agency was already secretly collaborating with General Gutiérrez. Ralph Villarruel, a veteran D.E.A. agent who had been working with Mr. López, said he pursued suspects the general believed were in hiding in the United States and seized loads of cocaine moving across the border. In return, he said, the general allowed him "unbelievable access" to crime scenes, suspects and evidence. After Mr. Palma's arrest, Mr. López and General Gutiérrez let Mr. Villarruel make copies of names and numbers in the drug trafficker's cellphone. An appreciative Mr. Villarruel said he arranged with his bosses in Mexico City to award the general a special commendation. "We were doing things we hadn't ever been able to do, and I wanted to acknowledge that," Mr. Villarruel said, pulling out a photograph of the closed-door occasion. By December 1996, Mr. Zedillo elevated General Gutiérrez to run counternarcotics efforts as the director of Mexico's National Institute to Combat Drugs. The move was a victory for the administration of President Bill Clinton, which had put in effect the North American Free Trade Agreement and orchestrated a $50 billion bailout of the Mexican economy. Cracking down on drug traffickers hardly seemed too much to ask of the United States" neighbor. In General Gutiérrez, who had the face and demeanor of a pit bull, the United States saw the no-nonsense partner it had been seeking. The administration invited him to Washington for briefings, and the United States" drug policy coordinator, Gen. Barry R. McCaffrey, praised him as a soldier "of absolute, unquestioned integrity." It seemed a head-spinning turn of events for a little-known military leader who could count his suits on one hand and had never traveled outside Mexico. When the general asked Mr. López to be his chief of staff, though, he was apprehensive about moving to the capital. But the general insisted. "Going to work in Mexico City felt like falling into a snake pit," Mr. López said. I had a bad feeling about the whole thing. There's a Problem Less than three months later, Mr. López was in Guadalajara for the birth of a grandchild when he suspected something had happened to his boss. He had been calling General Gutiérrez for days without success. Finally, he got the general's driver on the phone. "I don't know where he is," the driver said, according to Mr. López. You shouldn't call here anymore. I can't talk on this phone. Perhaps they're already listening. What the hell, you need to know. There's a problem. Is it a bad problem? Mr. López asked. "It's global," the driver exhaled. When Mr. López hung up and called the military base in Guadalajara, the commander there summoned him to a "counternarcotics operation." "I didn't know exactly what was going on," Mr. López said, "but I knew that a trap was waiting for me at the base." He told his family to leave Zapopan and warned his aides to stay away from the base. For several days, Mr. López kept out of sight, camping out in abandoned barns and beneath bridges while the military seized his house and searched his belongings. On Feb. 19, 1997, the Mexican defense minister, Enrique Cervantes Aguirre, held a dramatic televised news conference and accused General Gutiérrez of using his authority to help protect Amado Carrillo Fuentes, a drug baron nicknamed "The Lord of the Skies," for his use of converted jetliners to move multiton shipments of cocaine. The defense minister said that when General Gutiérrez was confronted with evidence of the association, he collapsed from what appeared to be a heart attack. With checkpoints going up around Guadalajara, it seemed impossible for Mr. López to leave, and he was so well known he feared he could not hide for long. Borrowing a page from the drug trafficker's playbook, Mr. López went to see a plastic surgeon to alter his appearance. Using a false name, he handed the surgeon $2,000 in cash and got a face-lift. In Washington, the Clinton administration summoned Mexican diplomats, demanding to know why their government had not shared its suspicions about General Gutiérrez before his trip to the United States. Congress called on the White House to void Mexico's standing as a reliable ally in the drug war, a move that could lead to sanctions against a country buying up American exports. The episode threatened security cooperation between the two countries. The Justice Department ordered the D.E.A. to explain how it could have missed evidence that General Gutiérrez was dirty. The D.E.A. turned to Mr. Villarruel, who began looking for Mr. López. Most of Mr. López's staff members had disappeared, said Mr. Villarruel, who learned that the military had rounded them up for questioning and that some of them had been tortured or worse. "My sources were dropping like flies," said Mr. Villarruel, a veteran agent and native of East Chicago, Ind., who has family roots in Guadalajara. One day I'd be talking to a guy, the next day he'd be dead. The D.E.A."s message reached Mr. López in May 1997, just as he and his family thought they had run out of options. The scars around his face had healed and he had dropped 70 pounds, trading his "Vitamin T diet" - tacos, tostadas and tamales - for salads and turkey sandwiches. He had dyed his hair blond and shaved his beard. Still, he said he feared the military would eventually catch up with him. Meanwhile, his family was struggling with an even more pressing matter. The grandchild born around the time of the general's arrest was sick. Her complexion was turning blue and her breathing was labored. The family was so terrified of being discovered that it agonized for days before taking the child to the hospital. Doctors diagnosed pulmonary stenosis, which restricted the blood flowing to her lungs. She was breathing easier after surgery, but her father, David, was not. "I knew she was going to need a lot more care," he said. How could I take care of her if I couldn't even give her a home? Only 22, he was now the de facto head of a family on the run. For safety's sake, he was the only one who knew his father's whereabouts, a secret he hoped he could keep if the military found him. "I remember telling my dad, "If the military detains me, give me three days," " he recalled. The first day of torture would be the hardest. The second day, they might realize I was not going to tell them where he was and let me go. But if I didn't appear the third day, I might never appear again. Later that May, the D.E.A. opened an escape hatch, offering the family a haven in the United States and arranging work permits and visas. Making the trip were Mr. López's wife, three children, daughter-in-law and two grandchildren. The family members made their way to Utah, where they had a friend. Mr. López followed a couple weeks later. Wearing a navy blue suit and a fedora he bought for the journey, he arrived in the United States with a briefcase packed with his life's savings, $100,000, and visions of starting over. On the Run This January, Mr. López and his son Luis Octavio headed to Wendy's for a 99-cent hamburger special. When his son handed over two dollars for their order, a few cents short of the total, an embarrassed Mr. López had to tell him that he could not cover the difference. Money, or the lack of it, has been the hardest part of living in hiding, Mr. López said. His savings ran out long ago, and most employers are not interested in a 64-year-old man with no Social Security card or documented work history. He has tried day jobs as a dishwasher and a construction worker, but his back is not strong enough. Fortunately, he said, he has an eye for junk. He inherited it from his father, who ran a car battery repair shop. Mr. López has taken that talent up a notch, scavenging for discarded auto parts, office equipment and home appliances that he restores and resells. But it is always a skate across thin ice, and Mr. López wakes up many days with no money and nothing left to sell. His dire circumstances reflect a precipitous fall from his arrival in the United States as a prized informant. The inside account he gave to Mr. Villarruel and other D.E.A. officials amounted to a bombshell, according to former agents involved with the case and classified intelligence reports obtained by The New York Times. He claimed that the Mexican military was negotiating a deal to protect the cartels in exchange for a cut of their profits. Mr. López specifically accused several top officers of being involved, saying some had asked the cartels for $2,000 per kilogram of cocaine that passed through Mexican territory. As a down payment, cartel operatives delivered satchels packed with tens of millions of dollars to senior members of the military, according to Mr. López. He also accused American-trained counternarcotics units of allowing kingpins to escape during sting operations. "It is highly likely that military officials probably wanted to continue to profit from an ongoing relationship with the drug traffickers," concluded one intelligence report. Mr. López said he told the D.E.A. that he did not believe General Gutiérrez was among those conspiring with traffickers. But the intelligence reports suggested that the general had ties to the Juárez cartel, and that the relationship may have posed a threat to other military officers who were being paid by rival drug-trafficking organizations. By 1998, some of that information began appearing in Congressional briefings and newspaper reports, pitting the D.E.A. against the White House. It was inopportune timing for the Clinton administration, which was now applauding the general's arrest as proof of the Mexican military's commitment to combating corruption. The White House opposed any measures that would undermine the United States" second-largest trading partner. The D.E.A. accused Mexico of failing to live up to its security commitments, and it advocated taking action that could lead to economic sanctions. "There was definitely a split between us and the White House over Mexico," a former senior D.E.A. official said. Mexico, which was still trying to track down Mr. López, intensified its search in 1999. The Foreign Ministry requested Washington's assistance to determine whether he lived in the United States, a senior American federal law enforcement official said. United States marshals reported back that he did. Later that year, Mr. Villarruel asked Mr. López to meet him at a Denny's in San Diego. Mr. López could tell something was amiss when Mr. Villarruel arrived alone and had a hard time looking Mr. López in the eye. "I told him I had orders from Washington that I couldn't have anything to do with him no more," Mr. Villarruel recalled. I could tell there was some kind of pressure, but I couldn't tell if it was from Congress, or from Mexico, or where. All I knew was that if I had anything more to do with him, I could get in trouble. The orders meant that "from that moment, the agency wasn't going to protect me or my family," said Mr. López, who was shocked and confused. When Mexico ousted the Institutional Revolutionary Party in 2000, an era of multiparty democracy did not clean the slate. The new government officially charged Mr. López, issuing an arrest warrant, and promptly asked the United States to find him, former American officials said. Mexican officials discussed the matter with the American attorney general and the secretary of state at the time, John Ashcroft and Colin L. Powell, according to D.E.A. memos and e-mails. Federal marshals received two to three calls a day from the Mexican authorities asking how close they were to detaining Mr. López, one memo shows. Mr. Villarruel implored the D.E.A. to ignore Mexico's extradition request. Mr. López is "one of a few individuals remaining who can provide extremely damaging information on high-level, drug-related corruption within the Mexican government," Mr. Villarruel wrote to his bosses. He warned that "if López Vega is returned to Mexican authorities, it is highly likely that López Vega will be tortured and/or killed." But D.E.A. officials refused to interfere with the arrest warrant. Defying orders, Mr. Villarruel warned Mr. López to watch his back. About five months later, Mr. López was meeting his sons at a relative's house in California when he noticed suspicious people hanging out in the neighborhood. He immediately jumped in a car and sped away. Seconds later, SWAT teams, canine units and helicopters from the federal marshal's office descended. Officers tried to catch up with Mr. López but failed. "I had a 20-second head start," Mr. López said. When you're on the run, 20 seconds is a lot of time. Adjusting to a New Life As Mr. López and his family contended with their new lives in the United States, a story with similar twists and turns began playing in movie theaters across the country. The film, "Traffic," was hailed as a landmark for dissecting the cross-border forces driving the drug war. It featured the United States pinning its hopes on a mercurial Mexican general, inspired by General Gutiérrez, who is later caught working for the cartels. The general was allied with a Mexican police officer, played by Benicio Del Toro, who crosses the border and gives information to the D.E.A. The character was a composite of informants developed with the help of a D.E.A. consultant and was not modeled on Mr. López, whose existence has never been acknowledged by the American government. The film ends with the officer returning to Mexico and using the money the agency paid him to have lights installed at a baseball field in a poor neighborhood. Off screen, the real-life version headed in an unhappier direction. After Mr. López went into hiding, the American government revoked his family's visas and work permits, forcing them into their own kind of stealth existence among Utah's growing population of Mexican immigrants. Mr. López's wife, Soledad, suddenly had to fend for herself, learn English and get a job. Their daughter, Cecilia, began drinking and dropped out of college, hoping that if she rebelled enough her father would return. The couple's sons, David and Luis Octavio, managed the family's affairs and bore the brunt of the psychological trauma. "We're all damaged," said Luis Octavio, 35. We don't talk much about the times when we wish we could run away from our situation. But we've all felt that way. In the aftermath of the raid in California, the brothers fended off questions from federal marshals who pointed guns in their faces and threatened to deport them unless they revealed their father's location. For the next few years, the elder son, David, followed his father into hiding, rarely seeing his own wife and children. His movements underground were like something out of a spy novel. By day, he worked odd jobs. In the evenings, he ducked into gas stations, changed clothes and hired taxis so he could see his father without being followed. He created a code for their pager communications and rented places to hide. "I promised him I would stand by his side until this whole thing was over," recalled David, 38. I had no idea it would go on for so long. In Utah, Luis Octavio worked two jobs to help support his family. Because he had married an American after arriving in Utah, he did not have to worry about deportation. But he tried to find a legal way out of the ordeal for the others. In 2002, he met with the same federal marshals who were looking for his father, hoping to make the case that the elder Mr. López had been betrayed by the D.E.A. One marshal, Michael Wingert, told Luis Octavio that he sympathized, but that the United States could not shield his father from the Mexican charges, according to a recording of the meeting made by Luis Octavio. "We can only assume with a case like this that your dad's got some enemies in really powerful positions in Mexico, and they want him back," Mr. Wingert said. Several years later, in 2007, the López family made their own power play. They shared their story with aides to Senator Orrin G. Hatch, the former chairman of the influential Judiciary Committee. The senator's staff members in Salt Lake City would not comment on their role, except to say that they referred the matter to the Justice and Homeland Security Departments, which helped the family obtain political asylum in 2011. By then, David had returned home to Utah, where his wife gave birth to their third child. With no consistent work history, he has not been able to find a full-time job. Luis Octavio got a bachelor's degree and a recruitment job at a college. But his family's history continues to hold him back. Last year, when he was profiled in a local newspaper as a model of how much Mexican immigrants have contributed to Utah, he lied about why his family came to this country. When approached about possibly taking a business trip to Guadalajara recently, he was tempted to go, if only out of defiance. "I feel a tremendous sense of impotence," he said, "and the only tool I have to cope with that feeling is to separate myself, and act like my father's situation doesn't exist." The Pursuit Continues Mr. López had settled into a booth at McDonald's one recent morning when his cellphone rang. A woman on the line said she had a recorded message for him. The next voice he heard belonged to General Gutiérrez. They tried to finish me, but they didn't succeed. I'm still here," the general said, his voice barely above a whisper, according to Mr. López. General Gutiérrez, 88 and suffering from terminal prostate cancer, was speaking from a bed in the same military hospital where he had collapsed after his arrest 16 years earlier. He has not quite served half of his 40-year sentence, but he had been released from prison and his relatives said his rank had been restored so that he could receive military medical care. "They haven't left us with much," the general told Mr. López, "but we must protect the little we have left." In January, the Mexican government once again raised Mr. López's case with the American authorities, according to a Mexican official. The Justice Department asked for confirmation that the charges against Mr. López were still valid, and the Mexican government is expected to report back within the coming weeks, the Mexican official said. "Until then," he said, "the case is not closed, as far as we are concerned." The Justice Department and the D.E.A. said they could not comment on a case that involved a confidential informant. But an American law enforcement official who has fielded some of Mexico's requests said Washington was stalling for time, hoping the charges would be dropped. The United States is no closer to understanding whether Mr. López is guilty or the target of Mexican officials who wanted to silence him, the American official said. "If it was up to us, we'd make this case go away," the official said. But if Mexico decides it still wants him, I'm not sure how the United States is going to say no. Security cooperation between the United States and Mexico has been strained since December, when Enrique Peña Nieto began his term as president of Mexico. His administration believes that his predecessor, Felipe Calderón, allowed the United States to play too big a role in setting Mexico's security agenda and in staging law enforcement operations, officials in both countries said. The Obama administration has struggled to negotiate new terms of cooperation, the officials said, and President Obama is scheduled to travel to Mexico this week. Meanwhile, the violence that has left about 60,000 people dead over the past five years rages on. And the military has been so demoralized by accusations of corruption and human rights abuses that some of its leaders openly wonder whether to pull out of the fight against drug traffickers. Mr. López religiously tracks these developments during his morning coffee breaks at McDonald's, looking for clues that might help him make sense of his own situation. Mr. Villarruel, now retired from the D.E.A., is one of his few contacts from his former life. Mr. López said he sees public attention as his only hope for a return to something resembling a normal existence. "For better or worse, it's time that I defend myself," Mr. López said. When asked what he would do if he ran out of money, Mr. López shrugged and said he would figure something out. He compares himself to Prometheus, the Greek mythological figure whose punishment for stealing fire and giving it to humans was to be tortured, surviving only to face the same torment the next day. "Every day is like the first day for me," he said. From the moment I wake up until the moment I lay down, I am thinking, thinking, thinking about what happened to me. I try to make sense of things that don't make sense. And it eats away at me. And it eats away at my family. Then the next day, I wake up and start all over again. Karla Zabludovsky contributed reporting, and Lisa Schwartz contributed research.