The Rio 2016 gold medallist - who has also won the Las Vegas, London and Rotterdam marathons - was given a four-year ban in 2017 for testing positive for the blood-boosting drug EPO.
Sumgong denied any wrongdoing and claimed she must have been given the banned substance by an "impostor" during a doctors' strike at a hospital in Nairobi.
The 34-year-old Kenyan was visiting the hospital, she said, for treatment for a ruptured ectopic pregnancy.
That story, however, is now in tatters after a joint investigation between Anti-Doping Kenya and the Athletics Integrity Unit discovered there was no record of her hospital visit, the documents she produced to corroborate her story were fake and the 'whereabouts' details in her anti-doping profile placed her five hours' drive away.
Medical experts also pointed out that EPO was a very unlikely treatment for her claimed condition and she would have been hospitalised for at least four days.
The disciplinary panel was chaired by Michael Beloff QC and, in a 33-page written decision, he poured scorn on Sumgong's story.
"To put the matter colloquially, she could not be in two places at once," he wrote.
"(And) the athlete's 'evolving' - to borrow the AIU's euphemism - explanations for her (positive test), coupled with her later failure to engage with proceedings at all, must also tell strongly against her."
The upshot is that Sumgong's attempts to deceive the IAAF amount to a second anti-doping charge of "tampering", which doubles her initial ban. She had started that sanction in April 2017 but the new, extended ban starts now, meaning she has effectively been banned for 10 years.
In a statement, AIU head Brett Clothier welcomed the decision and said: "We hope it sends a message to dopers that the AIU has strong investigative capabilities and does not tolerate false evidence in doping cases."
As things stand, though, Sumgong can keep her pre-2017 results, and the only way that will change is if one of her stored samples tests positive in future rounds of re-analysis. The International Olympic Committee, for example, can retest any of her Rio samples until 2026.
