The secretary-general of Interpol, Ronald K Noble, may have thought he had little to fear from the Belarusian mother whose son was shot dead after he and a friend confessed to planting a bomb that killed 15 people on the Minsk underground system last year. But Lyuba Kovaleva is fighting a campaign that has raised grave questions about Mr Noble's judgment, and is lending weight to claims that the Belarusian secret police, the KGB, planted the device, rigged a show trial and tortured confessions out of the two suspects.
The tale begins two days after the metro bombing in April last year. President Alexander Lukashenko – routinely called the "last dictator in Europe" – announced on TV that, thanks to a KGB investigation, two men had confessed to the crime. He said they would face "the most extreme punishment". The men were Ms Kovaleva's son, Vlad Kovalev, and his flatmate – the alleged bomber – Dima Konovalov.
A month later, Mr Noble, an American, arrived in Minsk and held a press conference where he is said to have compared the metro attack to the bombing of London's transport network on 7 July 2005. He called Mr Konovalov "a terrorist" and praised "the high professionalism" of the Belarusian criminal investigation for solving the case "so quickly".
The trial of the two suspects began four months later. They were found guilty in November and in March this year both were executed with a bullet to the back of the head. Mr Noble has been accused by opposition figures in Belarus of abandoning the presumption of innocence until proven guilty, leaving himself open to the charge of being Mr Lukashenko's "useful idiot" – criticisms Interpol hotly disputes.
In Vitebsk, three hours east of Minsk, I met Ms Kovaleva. A slight, frail woman racked with grief, she said she was often watched by the KGB but that the coast was clear that day.
"The court has not a single piece of proof of guilt, not only of my son – who was dragged into this – but also of Dima Konovalov, apart from Dima's confession, which he gave under torture," she said in response to the official version of events – that the men had a fair trial. "They were beaten to such an extent that when we were shown the video recording of Dima being interrogated, he could barely speak. He could barely sit."
Opposition activists both inside and outside Belarus have claimed they were tortured at KGB headquarters in central Minsk. The building is known as the "Amerikanka" and is said to be named after a 1920s design for a Chicago prison. People who say they have been tortured in the Amerikanka include the opposition figures Vlad Kobets and Natallia Radzina, the presidential candidates Andrei Sannikov and Ales Mikhalevich, the poet Vladimir Neklyayev, and others still in Belarus. They say that in December 2010, after a bitterly disputed election, victims were forced to strip naked and stand in stress positions while masked guards swished electric batons. Icicles hung from open windows and the temperature outside was -20°C.
As part of my investigation, I went to a freezer warehouse in North London to experience it myself. I stripped off and stood in the Amerikanka stress torture position, described by the opposition, for as long as I could bear. Opposition activists say they had to endure 40 minutes. I lasted 40 seconds.
In 2004, a European parliamentary report blamed the Lukashenko regime for the disappearances of four political rivals and raised the possibility that they were killed by death squads. Following an investigation by the BBC, it is understood that 30 more than people, mainly gangsters and other undesirables, were killed on the orders of the state. Mysterious suicides of political opponents are also common.
In the case of the Minsk metro bombing, Ms Kovoleva said her son and his friend never stood a chance of a fair trial. "On 13 April at 9am on the radio, I heard Lukashenko's announcement that the culprits had already been arrested, and that they would receive the harshest punishment – they would be shot," she said. "He said the boys had been interrogated and by 5am they had already confessed."
Mr Noble seemed unaware of the KGB's reputation for torture when he made his comments in support of the Belarusian investigation into the atrocity last year.
"I can tell all the citizens of Belarus that this case was solved so quickly because of the high professionalism of the police and officials in the Ministry of Internal Affairs and other ministries, because of the technology and CCTVs that you have in place," he said.
He noted alleged fingerprint evidence, which led him to call suspect Dima Konovalov "a terrorist".
According to Ms Kovoleva, it is not only the methods of interrogation used by the KGB which raises questions about the fairness of the men's trial. She claims that the CCTV evidence praised by Mr Noble was not credible. "The FSB [the Russian security service which was invited to help with the Belarusian investigation] analysed it for the court and said it was edited," she said. "The FSB also found that the photograph of the man with the bag in the metro, and Dima, were not the same height or complexion."
Ms Kovoleva explained that the man with the bag and Mr Konovalov were different people and at the trial there were three bags of different colour, size and weight. She said: "Where exactly the bag was, the court could not establish – or, indeed, whether there was a bag at all. [There was] no piece of the bag, or fragment of a lock or metal. If there was a bag, no remains of [it] were found in the remains of the explosion."
Closer scrutiny of the CCTV footage endorsed by Mr Noble, filmed minutes before the bombing at 5.56pm on 11 April 2011, reinforces these questions. When the bomber enters the metro, it is not clear whether it is Mr Konovalov or someone completely different. The person is carrying a black bag with a white mark on it. Five minutes later, the mark is no longer there.
State prosecutors claimed that Mr Konovalov was present when the bomb went off but, according to Ms Lyubov, no particles from the explosion were found on either suspect. The state also said he had walked back to his flat by 6pm – a journey of four minutes. I walked it, and it took me 26 minutes.
Natalia Koliada, co-founder of the Belarus Free Theatre, is an opposition activist who was herself locked up by the KGB and now lives in exile in London. She not only believes that the two defendants were innocent, but blames the secret police.
"This was a KBG bomb," she said. "There are no facts whatsoever to prove something else."
Mr Noble was not available for interview yesterday. A spokesman for Interpol denied that the presumption of innocence was breached in the case and disputed my conclusions about the evidence.
It said in a statement: "Ronald K Noble, Interpol secretary-general, concluded that the Belarusian criminal investigation was professionally conducted and that the arrests of Dmitry Konovalov and Vladislav Kovalev solved the case of who was criminally responsible for the bombing.
"Secretary-general Noble stands by that statement today … Advancing one-sided false claims about murderous terrorist conduct can only undermine public confidence in the media."
Meanwhile, Lyubov Kovoleva says that the state refuses to tell her where her executed son lies buried. "They are torturing me still," she said.
The lawyer-turned-opposition politician languished in Amerikanka for two months after KGB agents arrested him following protests against the election in December 2010 in Minsk. He was released in February 2011 but only after he signed a statement saying he would co-operate with the KGB and tell no one about what happened to him. He later retracted the statement and claimed to have been tortured.
According to witnesses, the poet was beaten severely at about the time of the election protests in 2010. He was taken to hospital but his injuries did not prevent KGB agents from reportedly bundling him out of his hospital bed in a blanket. He was taken to the Amerikanka and not heard from for eight days.
John Sweeney's report 'Torture In The 21st Century', will be broadcast on BBC Radio 4 at 11am today and on BBC2's 'Newsnight' programme at 10.30pm. His e-book, 'Big Daddy: Lukashenka, Tyrant of Belarus' is published by Silvertail Books