Houston man sentenced to death in China over drug trafficking charges An advocate says there's been no evidence tying him to the drugs.

An American man has been sentenced to death in China over an alleged drug trafficking plot.

His death sentence comes after spending six years in a Chinese prison.

Mark Swidan, an artist from Houston, has been detained since 2012, when he went to China for home flooring and fixtures, his mother Katherine Swidan told ABC station KTRK.

The sentence was passed down on Tuesday by Guangdong Province Jiangmen Intermediate People's Court. The court announced that Swidan, who they identified only as "Mark (American)," was handed a suspended death sentence, which usually evolves into life in prison.

"The number of drugs sold and manufactured was extremely large. The crimes were extremely serious," reads a translated version of the statement from the court. However an advocate for Swidan says there's been no direct evidence tying Swidan to the drugs.

A U.S. State Department official confirmed the sentence to ABC News and said that U.S. consular officers "have been providing all appropriate consular services."

"We have visited him monthly since his arrest and will continue to visit regularly," the State Department official told ABC News.

Katherine Swidan told KTRK that she is "still in shock" over the sentence of her son, who is now 44 years old.

"I haven't slept, just not believing this," she said.

John Kamm, the executive director of the Dui Hua Foundation, a non-profit advocacy group based in San Francisco that works to improve treatment for detainees in China, told ABC News that he has worked on Swidan's case "for many years."

In a statement summarizing the case, Dui Hua Foundation officials say that drugs were found on Swindan's interpreter and driver, but no drugs were ever found on Swidan or in his room. The statement says that no forensic evidence has ever been produced connecting the American to the drugs or any trafficking.

"At the hour of Mark Swidan’s sentencing, American Treasury Secretary Mnuchin and Trade Representative Lighthizer were in Beijing to discuss a deal to end the trade war between the United States and China," Kamm said in a statement released through Dui Hua.

"Both countries agree that the ultimate success of any agreement to end the trade war depends on enforcement in a system based on judicial transparency and due process. The Swidan family was never told why the judgment was repeatedly extended, a violation of a basic norm of transparency. Mr. Swidan’s rights to a fair trial and due process have been seriously abused. This is a sad day for justice in China," Kamm said in the statement.

ABC News' Karson Yiu and Conor Finnegan contributed to this report.