Caster Semenya took to the track three times on Saturday and with every stride suggested she was hurtling back towards the extraordinary. First she won the South African 400m title in 50.78 seconds, not only the fastest time in the world this year but a personal best by nearly two seconds. Then, after a 50‑minute rest, she coasted to the 800m title in 1:58.45, another world’s best in 2016. Finally, for good measure, she romped home in the 1500m.

It was the first time anyone had won three South African titles in a day but it was the manner of their achievement which left the deepest impression. Semenya barely broke sweat in each race until the home straight. As the TV commentator in the 800m, which she won by seven seconds, put it: “My word this is something special. She is jogging!” As the renowned South African sports scientist Ross Tucker put it: “It’s impossible to know how quickly she could have run but it looked so easy. She looked capable of running in the low 49-seconds for 400m and the 800m in 1:55 or faster.”

Predictions are a dangerous business. But Semenya appears a red-hot favourite for 800m Olympic gold. And, if that happens, many of the controversies which raged in 2009 – when her crushing world 800m title triumph was overshadowed by accusations and insinuations about her gender – will again swirl around Rio like a tornado.

After that victory, by more than four seconds, the 18-year-old’s world changed and largely for the worse. She was subject to gender tests which were never made public but were alleged, according to the Australian Daily Telegraph, to show she had no womb or ovaries but had internal testes. The IAAF, athletics’ governing body, was accused of violating her human rights, gross insensitivity and even racism. It insisted it was merely trying to ensure women with higher testosterone did not have an unfair advantage. Arguments flared, subsided and flared again; Semenya mostly suffered in silence.

Since then she has been very good rather than great. There were silver medals at the 2011 world championships and the 2012 Olympics, which may yet be upgraded given the Russian Mariya Savinova, who beat her both times, is facing a life ban. But after struggling at the world championships last year, Semenya has suddenly rediscovered her mojo – and her motor. As Tucker says: “She looks ridiculously lean and athletic. She’s a different athlete compared with last year.”

So what has changed? It is probably down to not only her training but a decision in a Swiss courtroom. The fallout from Semenya’s case in 2009 made the sporting authorities replace their “gender testing” policies with an upper limit for women athletes’ testosterone levels – with anyone above it required to take hormones to lower them to more ‘normal’ levels to compete. Yet in July the Court of Arbitration for Sport reversed that rule after considering the case of the Indian sprinter Dutee Chand, who was due to compete at the Commonwealth Games until discovered to have high testosterone.

Chand’s lawyers insisted she was not to blame for her genetic advantages, just as some basketball players cannot help being seven foot tall. They also claimed that the existing law was discriminatory against women, because men are not screened for high natural testosterone levels. However, as Dr Marjolaine Viret, a Swiss-based attorney in sports law who frequently deals with CAS arbitration explains: “The decisive factor for the CAS panel was whether testosterone above the 10nmol/L threshold set by the IAAF gave female athletes a competitive advantage over their fellow competitors, which brought them within a range comparable to male athletes. Here the burden of proof was declared to be on the IAAF.”

Given the lack of sufficient scientific evidence, the existing hyperandrogenism regulations law was suspended for two years – allowing any female athlete on testosterone‑suppressing medication to come off it. Tucker, for one, thinks CAS’s decision was wrong. “The old rule was a workable compromise with a scientific basis,” he says. “It was an attempt to manage a difficult situation and CAS have effectively removed the management. Now there’s no regulation and ultimately this changes the nature of women’s sport.”

He believes there is another flaw in its verdict. “CAS were also saying that testosterone you inject is different from testosterone your body produces, which is ridiculous because it’s the same thing.”

This, and other arguments around athletes’ rights, are often difficult to weigh up but for Tucker the key question is when does being an outlier become a problem and exceptional become unfair. “That’s the crux of the issue. We say you can and should have certain advantages if you want to win but at some point the type of advantage you have, and its magnitude, must be checked. For a middleweight boxer, this happens at 75kg. But for men versus women, it happens somewhere. We just don’t know where.”

Meanwhile Semenya’s gaze is firmly focused on better times ahead. “I am a dreamer,” she says. “And what I dream of is to become Olympic champion, world champion, world record holder.”

All three goals appear tantalisingly within her grasp, including Jarmila Kratochvilova’s once seemingly impenetrable 800m world record of 1:53.28. Yet however bold her attempts to make history, one fears she will never completely outrun controversy.