Kiprop was promoted to Olympic gold in 2008 after a positive doping test saw original winner Rashid Ramzi disqualified the following year.
Add in the fact the World Anti-Doping Agency revised its code in 2015 to extend the statute of limitations for retesting from eight to 10 years.
The Beijing Olympics were held from August 8-24, 2008.
The Herald understands Kiprop's sample sits in a Beijing Games batch within a Lausanne laboratory. It would need re-testing before August 19 this year, a decade after the 1500m final. Otherwise it becomes legally unusable.
Unless urgent action takes place, Willis' chances of joining Jack Lovelock, Sir Peter Snell and Sir John Walker as New Zealand's fourth Olympic 1500m champion appear limited, at least officially.
In a statement released via his lawyer, Kiprop claimed he wired funds to one of the doping control officers by mobile phone while they were still in his house in Iten, Kenya last November. He learned the sample was positive in February.
"I remain perplexed on how my innocent sample could turn positive on the only time when money was extorted from me," he said.
"It is not beyond my suspicion that my sample turned positive because I might have remitted less money than was expected to remit."
Kiprop's statement did not specify what substance he tested positive for, but suggested it might be the blood-boosting hormone EPO.
"I am told EPO is put into the body using injection," he said.
"The last time I had an injection was in 2014 when I was given a yellow fever vaccination before travelling to Bahamas for a competition."
Kiprop's failed test deals another blow to Kenya's middle and long-distance running reputation. Dozens of his compatriots have tested positive for an array of banned substances in recent years.
Willis described any potential upgrade to a gold medal as a "moot point" when interviewed yesterday by the Herald.
The 35-year-old said that having already endured the Ramzi saga, he preferred to reflect on the joy taken from an elite running career spanning most of this century.
However, he said it was "very important" justice was served for any doping violations.
"The public and fans have every right to assume a high percentage of everyone is on it [banned substances].
"I don't judge anyone for casting doubt on anyone in races, including me, because that's how poor our sport has done the job at keeping clean. That's the most frustrating part.
"The most important thing is for them not to be afraid to bring down the biggest names, if and when they cheat. They've got to be prepared to take a blow to the image of the sport - not that it could be any lower - so it can be rebuilt."
