Olympic history is being rewritten thanks to the International Olympic Committee's (IOC) practice of retesting urine samples taken from athletes at the 2008 and 2012 Olympic Games.
The IOC, which stores samples for 10 years, has reanalysed more than 1,000 samples from the Beijing and London Olympics with improved techniques that can detect the use of steroids going back weeks and months, rather than days.
Of the 98 samples which have come back as positive so far 49 belonged to athletes who were awarded medals at those games.
HOW THE PROCESS WORKS
By the end of any Olympics, IOC testers are in control of as many as 5,000 urine samples.
Samples are divided into "A" and "B" bottles, and the "B" samples are available in case they're needed to corroborate a positive result in the "A" bottle.
The initial tests take place in the lab located in the Olympic city. Because of the huge number of samples and tests that need to be conducted in a short period of time, not every sample is tested for every drug. Experts take educated guesses on which set of athletes are more likely to use certain drugs and run the according tests.
After those tests, the leftover urine is placed into a cargo container that's refrigerated, then loaded on an aeroplane that goes to the Swiss Laboratory for Doping Analyses in Geneva.
If a test for a certain drug wasn't completed at the Olympics, it can be done in a retest years later.
"The anti-doping guys have an arsenal that they don't make public," said Tom Brenna, a Cornell University professor and an expert on anti-doping laboratories.
An example Brenna gave was the discovery of a test for plastic residue from the bags some cyclists used for EPO-laden blood transfusions. Because EPO has been notoriously difficult to detect, the test for the "plasticiser" gave the drug-fighters a backdoor method to prove someone was using the drug.
The IOC notifies the national Olympic committee of any athlete caught due to subsequent retests. Athletes found guilty of doping and stripped of medals. Any reallocation won't take place immediately, first the IOC will retest the samples of those athletes who stand to move up in the medals to make sure they were clean.
THE 2016 SHAME FILES
Athletics (track): 18