Last year, Francisco Dall'Anese came into possession of a series of photographs. They were purportedly taken at El Pavon Prison, just outside Guatemala City, on 25 September, 2006, and appeared to show, in sometimes graphic detail, what happened when 3,000 police and soldiers tried to seize back control of the compound from inmates who had mounted an uprising against their guards.
During the raid, which came amid rumours that crack cocaine laboratories were operating on the site, seven inmates were killed. One of them was Luis Alfonso Zepeda, a powerful gangland boss said to have organised the uprising. Authorities claimed that he died in a desperate battle, firing machine-guns at the men attempting to reassert law and order.
But the photographs told a different story. One, for example, showed Zepeda in police custody, shortly before he was killed. He was wearing a brown shirt and appeared to be obediently following orders to disrobe. Another showed him just after he died, for some reason wearing a blue top. A third picture showed a different dead inmate; he had been shot several times in the torso, yet his shirt did not contain a single bullet hole.
Mr Dall'Anese quickly came to a conclusion: there never had been a brutal, 90-minute gunfight, as authorities had claimed. Instead, the seven inmates had been rounded up, stripped naked, and executed in cold blood. Their bodies were then dressed in fresh clothes, and arranged to give the impression of a struggle. This was, he decided, an obvious example of a crime sadly commonplace in Guatemala: extra-judicial killing by uncompromising officials.
The cover-up was, he adds, spectacularly poorly-staged. A single bullet was put through each window pane of the building where they allegedly died. "Each shot hit exactly in the centre," he laughs. "In a real gun battle, you'd never see such marksmanship." And the person responsible? "He's right here," adds Mr Dall'Anese, flicking to a photo of an overweight, middle aged man, with grey hair, standing at the scene.
The man is Carlos Vielmann, and he is Guatemala's former Interior Minister. In August last year, he was charged with ordering the extra-judicial murder of the seven prisoners. He was also charged with the illegal killing of three inmates who had escaped from the country's El Infiernito prison, in a separate but no-less-ugly incident in 2005. Vielmann was arrested in Spain shortly afterwards.
His extradition has been approved, though prosecutors are currently working out whether the interests of justice would be better served by holding his trial in Europe. He claims to be innocent of all charges, arguing, among other things, that it is impossible to prove when the superficially-incriminating pictures were actually taken. The case, as they say, continues.
So it goes in the extraordinary day-job of Francisco Dall'Anese, an earnest Costa Rican lawyer who works out of a heavily-fortified colonial mansion in Guatemala City, protected by 30ft razor wire fences, and armed guards who force visitors through metal detectors and X-ray machines. Part-detective, part lawmaker, and part prosecutor, he is tasked with cleaning up one of the most corrupt, crime-ridden, and dangerous countries on Earth.
Mr Dall'Anese leads the Commission Against Impunity in Guatemala [CICIG], an elite unit of foreign investigators, employed by the United Nations, who arrived in the country in 2007. In a bold experiment in turning round failed states, their remit is to disrupt the crime networks which have their tentacles wrapped around almost every tier of government, from the police and judiciary to its industry and politicians.
The history behind their appointment is long and complex. But it boils down to this: financed by the $10bn-a-year cocaine trade which courses through its borders, criminal gangs have for years been able to operate in the Central American country with impunity. Judges throw out prosecutions, on spurious "technicalities". Police refuse to investigate thefts, extortion rackets, official fraud, and even deaths. Roughly 96 percent of all murders currently go unsolved.
Four years ago, Guatemala's government reached out to the UN for help, having decided, in the words of former vice president Eduardo Stein, that "asking the justice system to reform itself was like tying up a dog with a string of sausages". CICIG was duly established, and its work is perceived to be so successful that Honduras, El Salvador, and Belize are currently considering plans to introduce similar UN-backed teams of prosecutors.
Mr Dall'Anese has 207 members of staff, hailing from 23 countries. They dig through official paperwork and listen dutifully to anonymous telephone tips from members of the public. They propose new laws, and massive reforms. At their behest, former President Alvaro Colom fired 1,700 corrupt police officers, and six judges from the Supreme Court. At any one time, they have dozens of investigations running, several of which have recently resulted in high-profile success.
Last year, CICIG uncovered a crime ring of public officials, judges, and orphanages, who were kidnapping small children from poor families, falsifying their birth records, and fast-tracking paperwork which allowed them to be illegally sold for adoption in the United States. "We managed to get two very prominent public officials imprisoned," he says. "It was a huge achievement. We are talking about a business worth hundreds of thousands of dollars each year."
More recently, Mr Dall'Anese and his team solved the bizarre killing of Rodrigo Rosenberg, a high-profile lawyer who arranged his own assassination, and in an elaborate effort to frame former President Colom, left behind a video which accused the politician of his murder. The plan very nearly succeeded, but was uncovered using wire taps.
The work has made CICIG hugely popular among ordinary Guatemalans, who are weary of the country's soaring crime levels. Among them is Doryan Bedoya, a director of the charity Caja Lúdica, which works to prevent youths joining gangs. "In the past year, three of our graduates, and one member of staff have been killed," he says. "Not one of the crimes was even investigated. The police are either corrupt or lazy."
But taking on vested interests can be a dangerous business. Mr Dall'Anese almost always has a bodyguard at his side, while his colleagues are protected by 80 security experts. "There was a case recently of a public attorney who was kidnapped, tied to four cars with ropes, and literally torn apart. The perpetrators filmed it and sent it to other people at the attorney's office," he says. "Those kind of threats come with the job, and you try not to think about them."
More obvious threats are political. Mr Dall'Anese's predecessor, Carlos Castresana, was forced out of the job in June 2010 saying in his resignation statement that the country's government had failed to pass proper anti-impunity laws, and claiming that opponents had been circulating unfounded rumours about his private life. More recently, CICIG lost what seemed to be a cut-and-dried case against former President Alfonso Portillo, who was accused of embezzling $16.1m of public funds, after a judge dismissed the prosecution on a technicality.
"This was a very easy case, because a subordinate of Portillo stole the money and wired it to private accounts to his wife and family members. We had the documents to prove it. The fact that the case was thrown out frustrates me, but just getting Portillo to appear before a judge was unique."
Real justice may still be some way off, in other words, but they're making progress.