By Dave Graham
MEXICO CITY (Reuters) - Restoring order to a country torn apart by drug violence was Mexican President Enrique Pena Nieto's first promise when he took power two years ago, but corruption and police brutality have handed him the biggest crisis of his rule.
Local police abducted 43 trainee teachers in the southwestern city of Iguala on Sept. 26 and handed them over to a drug gang. The gang almost certainly murdered them and torched their bodies, the government says.
The case, still not closed, has infuriated Mexicans and highlights the scale of the challenge that Pena Nieto faces in trying to end shocking violence and impunity.
"What we're seeing are the results of many years of deterioration, complacency and denial by successive governments," said Eduardo Olmos, a former mayor of the northern city of Torreon, who purged all but one of its 1,000-strong police force in 2010 when it was infiltrated by the Zetas drug gang.
Such cases mean police are held by most Mexicans to be inept and massively corrupt, better known for breaking the law than for solving crimes. Last week, former President Ernesto Zedillo said the rule of law in Mexico is in a "really bad" state.
There are no easy solutions.
The country has thousands of different police forces, with each of about 2,500 municipalities, 31 states and the capital Mexico City boasting its own. Salaries run as low as 5,000 pesos ($370) per month, encouraging corruption, and training is poor.
Drug cartels and other gangs routinely buy off police to at least turn a blind eye to their operations, and sometimes to take part in murders and kidnappings, like in Iguala.
In Torreon, which lies at the crossroads of key smuggling routes, the Zetas recruited police for their war with now captured drug lord Joaquin 'Shorty' Guzman, whose henchmen controlled police in the neighboring city of Gomez Palacio.
When Olmos brought in an army general to clean up Torreon, the police rebelled, surrounding and occupying his office. He responded by ordering the entire force to take tests to prove their loyalty. All but one either failed the tests or deserted.
Even with a new force, purges continued for the rest of Olmos' term as mayor because the city struggled to hire clean cops and prevent them being corrupted.
In Iguala, dozens of local police have been arrested in the hunt for the killers of the 43 students, and the rest of the 380-strong force have been removed pending the investigation.
Iguala's mayor Jose Luis Abarca, his wife and its former police chief are suspected of masterminding the kidnapping of the students with local drug gang Guerreros Unidos.
Two decades ago, Guerrero was mired in a similar scandal when police massacred 17 farmers. Soon afterward, President Zedillo created a new, improved force, the federal police.
But problems persisted, and the federal police was accused of a spate of abuses under the presidency of Pena Nieto's predecessor, Felipe Calderon. In 2012, a group of them were charged with the attempted murder of two CIA operatives.
Zedillo's successors have one by one carried out their own police overhauls, with limited success.
Pena Nieto recently launched a military force within the federal police, or gendarmerie - albeit at barely one tenth of the size he had envisaged when he was running for president.
In a country where 98 percent of crimes go unsolved, justice is frequently non-existent. Hardly a week goes by without a new scandal. At the end of October, police were questioned over the slaying of three U.S. citizens in northern Mexico.
Experts say Mexico will not improve things without reform.
Only with a single, well-paid and properly-trained national force can there be effective policing, said Alberto Islas, head of consultancy Risk Evaluation. "That's the way to get control," he said. "A national gendarmerie, and that's it."
The new gendarmerie numbers about 5,000. But all told, there are more than 400,000 police across Mexico.
Still, a national force would weaken the power of 31 state governors who have become used to impunity, making it unlikely any time soon, said political analyst Fernando Dworak.
Some of Mexico's wealthier northern states, ravaged by cross-border violence, have attempted to tackle the problem by toughening their justice systems and improving police pay.
It has helped yield results, aided by government pressure on the bloodiest gangs like the Zetas.
Compared to 2011, when violence in the north peaked, murders in Nuevo Leon state fell 75 percent to 378 in the first nine months of this year. In Chihuahua they fell nearly two thirds to 828. Even so, they are still four times higher in Nuevo Leon and 2 1/2 times higher in Chihuahua than they were in 2004.
While Nuevo Leon offers police training for six months, some rural forces get just a few days, such as in the western state of Michoacan, where homicides are approaching a 16-year high.
Much of the responsibility for police corruption lies with their bosses, said Maria Elena Morera, head of Causa en Comun, a group dedicated to improving transparency and accountability.
"Why is someone who steals peanuts going to think it matters if the guy upstairs steals millions and nothing happens?," she said. "If the president wants to return the rule of law to the country, aside from strengthening the institutions, he has to clearly show he's cleaning the house from the top down."
So far, politicians have been reluctant.
An anti-corruption bill has been stuck in Congress for the past two years, and two former state governors indicted in U.S. courts for crimes including money laundering and drug trafficking have yet to be charged in Mexico.
(Reporting by Dave Graham; Editing by Kieran Murray)