How did Russia's doping programme beat the Sochi tests?

In 2014 Russia hosted the Winter Olympics in Sochi, and later investigations concluded that a state-directed system had been secretly swapping athletes' positive drug tests for clean ones. The World Anti-Doping Agency described doping among Russian competitors as state-sponsored and systematic, with the Russian state found to have supplied steroids and other drugs to athletes. Systematic doping has so far cost Russia and Russian-associated teams 51 stripped Olympic medals, four times as many as the next country.

The man at the centre was Grigory Rodchenkov, the director of the Moscow laboratory, whom WADA has called "the heart of Russian doping". He fled to the United States, and his account, documented in the film Icarus, was reported by The New York Times in May 2016. He said that doping experts collaborated with Russia's intelligence service. In his account, urine samples were passed through a "mouse hole" in the laboratory wall, tamper-resistant bottles were opened in a nearby building, and the samples were replaced with the athletes' own urine collected months in advance. He said that at least fifteen medalists at Sochi were involved.

Could that be believed? WADA asked Richard McLaren, a Canadian attorney, to investigate. His 97-page report, in July 2016, was limited to a 57-day window but found corroborating evidence in witness interviews, thousands of documents, hard drives and forensic analysis of sample bottles, including scratch marks inside the security bottles that are normally invisible to the naked eye. McLaren concluded "beyond a reasonable doubt" that the Ministry of Sport, the national teams' preparation centre, the FSB and the Moscow laboratory had operated a "state-directed failsafe system" he called the "disappearing positive methodology".

That system operated from at least late 2011 to August 2015 and was used on 643 positive samples, a number the authors consider "only a minimum". A second report found that more than 1,000 Russian competitors in summer, winter and Paralympic sports benefited from the cover-up.