More than two months after American distance runner Shelby Houlihan was given a four-year ban for using performance-enhancing drugs — a positive test that she blamed on a contaminated burrito — the Athletics Integrity Unit explained its decision in a 44-page report.

The AIU, the independent drug-testing arm of World Athletics, barred Houlihan from competing in the U.S. Olympic trials and the Court of Arbitration for Sport, the international body established to settle disputes in sport, handed down Houlihan’s four-year ban June 17.

On Wednesday, AIU released its report detailing the CAS judges’ decision and rationale in upholding its ban against the 2016 Olympian, who also holds American records in the 1,500 and 5,000 meters.

Houlihan, 28, will not be able to compete until January 2025.

The AIU report illustrates Houlihan’s attempts to use expert testimony, witness accounts, a hair sample and polygraph tests to prove that her eating a pork burrito from an Oregon food truck resulted in a false positive for the anabolic steroid nandralone.

The World-Anti Doping Agency had found in a 2020 study that trace amounts of the steroid can be found in boar meat and warned of the possibility of a mix-up, although the CAS panel found it “possible but improbable” that Houlihan’s burrito contained that meat.

World Athletics drafted its own expert witnesses to dispute Houlihan’s account, arguing that her “explanation presupposes a cascade of factual and scientific improbabilities, which means that its composite probability is (very) close to zero.”

In its report, CAS judges said that it was “possible but unlikely that the ingestion of boar offal would have resulted in the urinary concentration” of nandrolone found in her samples. The report also said that the hair sample and polygraph tests which Houlihan submitted were insufficient “to satisfy her burden of proving that the [anti-doping violation] was not intentional.”

While the ruling did uphold Houlihan’s four-year ban, it pushed back the start by five months, to Jan. 14, unless she successfully appeals to a Swiss tribunal.

Houlihan, one of the country’s best middle distance runners, last raced in December 2020. Later that month, she tested positive for nandrolone, an androgen that increases muscle mass, and whose illicit use has most commonly been associated with body builders.

Houlihan learned of her positive test and subsequent provisional suspension by AIU in January. Over the next six months, her camp challenged the punishment, citing a food journal to argue that the illicit substance entered her body when she ate the burrito about 10 hours before her test.

As the U.S. Olympic trials neared, Houlihan’s lawyers pushed the AIU to resolve her case so she could compete. In June, CAS handed down the four-year ban, keeping her out of the Tokyo Olympics.

“This ruling means that my goal of making another Olympic team is over for now,” Houlihan said in a June Instagram post. “I can’t begin to find the words to express how disheartening this is. It absolutely breaks my heart to have my dreams and career taken away for something I did not do. I will forge ahead with my appeal to the Swiss Federal Tribunal once the Court of Arbitration for Sport issues its reasoned decision. I am told that appeals of this kind are difficult to win, but I continue to believe that the truth will prevail.”

Since 2016, the U.S. Anti-Doping Agency has seen close to 30 proven cases of an innocent source — substances that may be picked up along the supply chain as meat or medication are produced and brought to market — having caused a positive. Paul Greene, Houlihan’s lawyer, told The Washington Post in June that the AIU denied a request to have another lab to look at her sample to determine if her explanation was feasible.

“There was never a second opinion sought,” Greene said. “You would think if you were going to ruin somebody’s life, you’d get a second opinion.”