(NewsNation) — In a locked cell, roughly 8,000 miles from his home just outside of Houston, Mark Swidan sits inside a Chinese prison.

For more than a decade, the businessman from Texas has been held captive on drug-related charges and currently faces a death sentence despite a lack of evidence.

“I was prayed out, cried out…and now I’m just mad,” said Katherine Swidan, Mark’s mother.

For Katherine Swidan, a few letters and some cryptic drawings are the only way she’s heard from her son in eleven years.

Mark Swidan’s nightmare in China started in 2012. The then 37-year-old and his fiancée bought a fixer-upper home that they planned to move into after the wedding. While searching for cost-effective ways of getting the materials to fix up their home, Swidan’s family says he found a factory in Guangzhou, China, where he could buy flooring and light fixtures for cheap.

“He said, ‘Mom, top-of-the-line leather chairs you can get for $200,'” Katherine Swindan said.

So Swidan hopped on a plane and went to China. On his last night in the country, Katherine says police raided his hotel room while he was on the phone with her.

“I heard glass break and a lot of commotion but I couldn’t pick out any words,” she said. “All I heard Mark say is, ‘What’s going on?'”

According to a United Nations investigation, Swindan was accused of colluding with a Mexican drug cartel to make methamphetamine, despite a lack of evidence. He was thrown into a detention center and eventually convicted. In 2019, he was sentenced to death.

Swidan, who is now 48, appealed his sentence. Earlier this month, it was denied.

Based on reports from a government official who recently met with Swidan, he has endured physical and mental abuse at the hands of Chinese authorities.

Katherine Swidan says her son has lost his teeth and more than 100 pounds. She said he’s been forced to sleep on cardboard in a cement cell with no heat or air conditioning.

“He would write and say ‘Mom, I’ve never been so cold in my life,'” she said. “For almost 11 years he’s slept with the lights on the whole time.”

U.S. lawmakers and the United Nations Human Rights Council consider his charges a farce.

But in recent months, other wrongfully detained Americans have garnered considerably more attention than Swidan who has spent more than a decade hoping for intervention and release.

In December, after nearly 10 months behind bars, WNBA star Brittney Griner was released from a Russian detention center in a high-profile prisoner swap. In March, Evan Gershkovich, a Wall Street Journal reporter, was arrested in Russia and accused of espionage.

Katherine Swidan feels like her son’s case has been overlooked.

“It’s like Mark doesn’t exist,” his mom said. “I think that the government is cherry-picking… I have never been contacted by Biden.”

Mark Swidan has now been stuck in China through three presidencies — former presidents Barack Obama and Donald Trump and current President Joe Biden.

Earlier this year, Texas Senators Ted Cruz and John Cornyn introduced a resolution on the Senate floor, calling on China to release Swidan.

Last week, the U.S. State Department responded to the Chinese court’s decision to uphold Swidan’s death penalty, saying in part: “We are disappointed by this decision and will continue to press for his immediate release and return to the United States… President Biden and Secretary Blinken continue to remain personally focused on the release of Mark Swidan and other U.S. nationals wrongfully detained or held hostage across the world.”

Until then, his mother is holding out hope that her son will eventually be released.

“He told me one time: ‘I’ll come home in a box of ashes or I’ll come home walking off a plane, Mom, but I will come home.’”