Shelby Houlihan, a double American record holder and the country’s best Olympic medal hope in middle distance running, is facing a four-year ban after testing positive for a performance-enhancing drug and will be barred from competing at the Tokyo Games. Houlihan forcefully claimed her innocence and blamed the steroid found in her system on a pork burrito she ate at an Oregon food truck.

Houlihan and her representatives announced the news of her test Monday evening, less than a week before the start of the U.S. Olympic track and field trials. Monday night, Houlihan blasted track and field’s drug testing apparatus as she pleaded her innocence.

“I feel completely devastated, lost, broken, angry, confused and betrayed by the very sport that I loved and poured myself into just to see how good I was,” Houlihan said in a statement on Instagram. “I want to be very clear: I’ve never taken any performance-enhancing substances, and that includes the one of which I have been accused.”

Houlihan’s explanation raises an issue of concern with the anti-doping community. As testing technology has improved to keep up with doping chemistry, it has threatened to sweep up innocent athletes along with the cheaters.

Tests can detect some substances in urine at levels 1,000 times smaller than they could 10 years ago. They can find drugs in an athlete’s system for much longer. But they also can discover trace amounts of substances that may be picked up along the supply chain as meat or medication are produced and brought to market. Since 2016, the U.S. Anti-Doping Agency has seen nearly 30 proven cases of an innocent source having caused a positive.

Houlihan’s case played out over the past six months and reached an apparent conclusion late last week, according to Houlihan and her camp.

In January, Houlihan learned she had recorded a positive test in December for nandrolone, an androgen and anabolic steroid that increases muscle mass. The athletes who most commonly use the drug illicitly are bodybuilders.

“It is not a substance any runner would take,” said Houlihan’s lawyer, Paul Greene, who has extensive experience representing athletes accused of doping.

“When I got that email, I had to read it over about 10 times and Google what it was that I had just tested positive for,” Houlihan said in her statement.

Relying on a food journal, Houlihan determined she had eaten a pork burrito about 10 hours before her test. The food truck where she purchased the burrito near her training headquarters in Beaverton, Ore., served pig offal, according to a statement from her coach. The World-Anti Doping Agency had found in a 2020 study that trace amounts of nandrolone can be found in that kind of meat and warned of the possibility of a mix-up.

The Athletics Integrity Unit, the independent drug-testing arm of World Athletics, placed Houlihan on a provisional suspension. As the U.S. Olympic trials neared, Houlihan’s lawyers pushed the AIU to resolve her case so she could compete. This past weekend, the Court of Arbitration for Sport handed down a four-year ban.

Houlihan said she had a hair sample tested and passed a polygraph test and that even WADA agreed the substance had not built up in her body, as would have happened if she took nandrolone regularly. She tested negative Jan. 23, Greene said, at which point the nandrolone would have still been in her system had she been injecting it to enhance her performance.

During the process, Houlihan’s camp asked the AIU to seek a second opinion, to ask another lab to look at her sample and determine if her explanation about eating pig offal was feasible. Greene said they were told it wasn’t necessary.

“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.”

In a statement, Bowerman Track Club’s Jerry Schumacher, Houlihan’s coach, called the case “a great tragedy in the history of American distance running.” At the news conference, Greene called the result “entirely unjust.”

“I do not understand how any competent and unbiased body could fail to conclude that Shelby is innocent,” Schumacher wrote. “Shelby was treated unfairly at every step of this process. … I believe if this had been USADA handling her case it would have been handled differently. At the very least, I’m confident she would have been treated fairly.

“Over the course of the past six months, I’ve learned more than I ever wanted to know about drug testing — about the procedures and organizations that govern our sport,” Schumacher added. “What I’ve learned has eroded all the faith I had in their ability to fairly serve and protect clean athletes.”

In a statement emailed to The Washington Post, Athletics Integrity Unit head Brett Clothier said each case AIU handles is “treated objectively in accordance with the WADA Code provisions.” Clothier said CAS will issue a full reasoning of its decision “in due course.”

Houlihan, 28, grew up in Iowa and attended Arizona State. She made the 5,000-meter final at the 2016 Olympics and won the national title in the 5,000 and 1,500 at the 2019 U.S. outdoor championships. She entered this summer as a threat to medal, especially in the 1,500 meters.

If upheld, Houlihan’s ban would last through the 2024 Paris Games and potentially wipe out the entirety of her Olympic prime. Houlihan could still appeal the ban in a Swiss court. It is highly unlikely that appeal could be heard in time for Tokyo, although an injunction may be a remote possibility. If an appeal is successful, it would probably happen in time for next year’s world championships.

“I have always wanted to be able to stand at the top of that Olympic podium with a gold medal around my neck knowing that I did that,” Houlihan wrote. “Now, I’m not sure I will ever get the opportunity to truly pursue that dream. I’m going to continue fighting to prove my innocence. I will not sit down and accept a four-year ban for something I did not and would not do.”

Monday night, Greene said he was heartbroken for Houlihan and called the case the worst of anti-doping. He knows skepticism follows athletes who fail drug tests, but he relayed a story that helped explain why he believes Houlihan.

At a meet in 2019, coaches begged Houlihan to wear carbon-plated track spikes, which can legally enhance a runner’s capacity. Houlihan finished fourth as she declined to wear them, beaten only by three runners who did.

“She wants to know how good she can be only on her own two legs,” Greene said.