Municipal and federal police officers confront each other in Monterrey, Mexico, this summer after federal authorities arrested dozens of officers from several towns who were accused of colluding with drug traffickers.
Reversing police corruption that has tainted whole departments, shattered faith in law enforcement and compromised one of society's most basic institutions is proving difficult, but not impossible.
The lie-detector team brought in by Mexico's top cop was supposed to help clean up the country's long-troubled police. There was just one problem: Most of its members themselves didn't pass, and a supervisor was rigging results to make sure others did.
When public safety chief Genaro Garcia Luna found out, he canned the team, all 50 to 60 members.
"He fired everybody," a senior U.S. law enforcement official said.
But the episode shows how difficult it will be for Mexico to reverse a legacy of police corruption that has tainted whole departments, shattered people's faith in law enforcement and compromised one of society's most basic institutions.
President Felipe Calderon's 3-year-old drug offensive has laid bare the extent to which crime syndicates have infiltrated police agencies at virtually every level. By blurring the line between crime fighters and gangsters, the rampant graft stands as one of the biggest impediments to the Calderon campaign.
Amid the raging drug war, Mexican officials are trying to fix the police through a hurried nationwide effort that includes better screening and training for candidates on a scale never tried here before.
At the heart of the overhaul is a "new police model" that stresses technical sophistication and trustworthiness and that treats police work as a professional career, not a fallback job.
In steps that are groundbreaking for Mexico, cadets and veteran cops are being forced to bare their credit card and bank accounts, submit to polygraph tests and even reveal their family members to screeners to prove they have no shady connections.
Across Mexico, hundreds of state and municipal officers have been purged from their departments and scores more arrested on charges of colluding with drug gangs.
But Mexico has a habit of trading in one corrupt police agency for another, and it will be a long, uphill struggle to create a law enforcement system that can confront crime and gain the trust of ordinary Mexicans. Until then, crooked cops undermine efforts to strengthen the rule of law and defeat drug cartels.
"If you don't have a safe environment to conduct investigations, then it's going to be extremely difficult to capture the narcos," said the U.S. law enforcement official, who was not authorized to speak publicly. "If you have state police that are corrupt and constantly feeding your movements, investigative movements, to the bad guys, you're not going to get anywhere."
Mexican soldiers arrest former Police Chief Jose Osiris Cruz Cabrera, left, and Cristian Jannet Perez Torres in Veracruz in September. They were among dozens held in connection with the disappearance of a customs official
Some people fear that the soaring drug violence and mistrust toward police could spark the formation of death squads or vigilante groups. Already there have been suspicions, though no proof, that dozens of killings have been committed by people taking the law into their own hands. More than 13,800 people have been slain since Calderon declared war on the drug cartels, according to unofficial news media tallies.
Although Mexican federal police are in charge of the crackdown against the cartels, it is at the state and municipal levels where law enforcement is most vulnerable, officials and analysts say. Drug gangs exploit hometown ties, dangle bribes and threaten the lives of officers and their relatives to turn police into a kind of fifth column.
Poorly paid state and municipal officers are often on the payroll of drug smugglers, passing tips, providing muscle or looking the other way when illegal drugs are shipped through their turf.
Criminal infiltration of local departments has worsened as the Mexican political system becomes less centralized and as narcotics traffickers delve into offshoot enterprises, such as kidnapping, theft and extortion, that under Mexican law fall within the jurisdiction of state authorities.
At times, local police have faced off in tense showdowns against Mexican federal police and soldiers. The mistrust often prompts federal authorities to keep their state and municipal counterparts in the dark, aggravating interagency frictions.
"There is a disorganized police fighting against organized crime," said Guillermo Zepeda, a police expert at the Center of Research for Development in Mexico City.
In the western state of Michoacan, 10 municipal officers were arrested in the slayings of 12 federal agents there in July. In the Gulf of Mexico port city of Veracruz, authorities investigating the June disappearance of customs administrator Francisco Serrano detained nearly 50 municipal officers. The then-chief of municipal police for the seaport and three traffic officers were later charged with his kidnapping. Serrano is still missing.
The profound flaws of Mexico's police, who are frequently ill trained, poorly equipped and unhappy in their work, are the most visible emblems of how the drug offensive is straining the nation's broader system of law and order.
An opaque and creaky court system groans under the weight of thousands of new drug war cases, and a number of prosecutors, defense lawyers and judges have been slain. Meanwhile, prison officials scramble to make room for the surge of detainees, many of them violent.
Calderon's administration has laid out a strategy to expand and revamp the federal police and to force states, cities and towns to modernize and clean up their forces through such tools as polygraphs and drug tests. Standing in the way are many years of graft, turf jealousies, budget constraints and a drug underworld that has greeted every government move with greater viciousness.
Garcia Luna, the public safety chief, has seized the moment to hire thousands of federal cadets, who under the strict new standards must hold at least a university degree. Despite the stiff requirements, the federal force has grown to 32,264 officers, from about 25,000 a year ago.
At a sleek federal campus here in the north-central state of San Luis Potosi, Mexican officials are rushing to turn 9,000 college graduates into federal investigators. The school boasts state-of-the-art lecture halls, computer rooms, workout facilities, a driver-training track and shooting range.
The U.S. government supports the push to expand and professionalize Mexico's federal forces, lending dozens of police instructors as part of a $1.4-billion aid package for Mexico known as the Merida Initiative.
Federal cadets, dressed in white polo shirts and smart bluejeans, study criminal procedure, interview techniques, criminology and intelligence. The school has graduated 2,234 investigators since June; more than 1,000 fresh recruits began the six-week course last month.
An even more daunting challenge waits in states and cities, which are home to the vast majority of police in Mexico -- more than 370,000 officers. In the last two years, the federal government has relied on budget incentives to prod local departments to vet officer candidates and boost salaries, now often as low as $90 a week.
Garcia Luna has gone so far as to call for eliminating the country's 2,022 municipal agencies, widely seen as the weakest link in Mexican law enforcement, and folding them into police departments of the 31 states and Mexico City, which is formally a federal district.
The proposal is controversial, probably requiring a change in the Mexican Constitution and facing opposition from municipal officials from across the political spectrum who are reluctant to yield parts of their fiefdoms.
Some analysts warn that such a plan could make it easier for criminal groups to bribe police.
"Concentrating power at the state level runs the risk of creating a more hierarchical, 'one-stop-shopping' system of high-level corruption," said David Shirk, a University of San Diego professor and a fellow at the Woodrow Wilson Center in Washington.
States and municipalities have moved inconsistently to clean up their forces. In some places, such as the northern city of Chihuahua, police are gradually adopting U.S.-style law enforcement standards, such as those promoted by the private Commission on Accreditation for Law Enforcement Agencies.
Many analysts are encouraged to see local agencies spending more to improve training, equipment and wages, but see scant improvement on corruption.
"You can train police all day long, but if they're still corrupt, then it doesn't really help," said Daniel Sabet, who teaches at Georgetown University and studies Mexican law enforcement. "The corruption and organized-crime infiltration has not changed."
Here in San Luis Potosi state, whose police operation is praised by the U.S. as among a handful in Mexico that are sound, officials raised minimum pay to about $700 a month and now offer bonuses of nearly two months' pay to officers who perform well and pass twice-yearly vetting.
Cesareo Carvajal, public safety director until the state government changed hands in September, said he fired about 150 of 3,000 officers during his two-year term.
The agency also bought radio equipment, new weaponry and police vehicles, and outfitted officers with redesigned uniforms to create an updated image.
At a state-run police academy where San Luis Potosi's next generation of police is being molded, the rhythmic thump-thump of boots on pavement echoed on a recent morning as officers-in-training practiced marching.
Cadets here say a new, trustworthy breed of Mexican police is possible -- but that it will take time to build.
As part of a stricter selection process, recruit Hiram Viñas was hooked to a lie detector and asked about any past scrapes with the law. Screeners peeked into his bank account and rummaged in his family's background.
Viñas, 24, wearing a blue windbreaker and buzz cut, said the rigorous scrutiny could help win over Mexican society.
"They are applying tests and evaluations now that had never been done in our country," he said. "I think over time, people will learn to trust the police again."
These are the videos from the confrontation between the federal police and the state and municipal police. They were pointing their weapons at each other and throwing punches. The potential for tragedy was high.