County police have repeatedly told Zhang to stop "running illegal massage and prostitution businesses," according to charging documents. In October 2012, a county detective and U.S. Homeland Security agents warned her she could face federal and immigration charges if she didn't comply, the documents said.
"The vice unit has conducted numerous search and seizure warrants at Jade Heart Health on the following dates," a Baltimore County detective noted in the documents, listing five dates between 2007 and 2012. "Detectives have advised Di Zhang numerous times to stop conducting such practices."
Even after Zhang and Dong were arrested in March, police said, the alleged prostitution continued — both at the original Jade Heart Health on Joppa Road and a new location on the 9100 block of Belair Road in Perry Hall.
Advocates say prostitution and trafficking cases can be difficult to prosecute — sometimes, sex workers are fearful of testifying, or penalties for those convicted are minimal. The charges Zhang and Dong face are misdemeanors, although human trafficking carries a penalty of up to 10 years in prison and as much as a $5,000 fine.
In 2007, Maryland strengthened its human-trafficking law, which prohibits transporting someone to a house of prostitution. And earlier this year, the General Assembly passed a new law authorizing the seizure of certain property owned by those convicted of human trafficking.
As the new state law was making its way through the legislature, though, federal authorities were already tracing the profits of Jade Heart Health, alleging that they went toward the purchase of four houses and one office building in North Baltimore's Charles Village and Oakenshawe neighborhoods.
"When individuals involved in criminal activities accumulate large amounts of proceeds," the federal agent wrote in the civil-forfeiture filing, "they attempt to legitimize the money through transfers between accounts and investments in various assets such as securities, stocks, and real estate."
The Baltimore buildings were bought by Zhang, her mother or their company, NIU Holdings, according to documents filed as part of the civil-forfeiture case. In several of the purchases, Dong also provided cash, according to the documents.
The properties were bought in 2011 and 2012 for a combined price of more than $956,000.
The forfeiture case makes no mention of Landmark Energy Enterprise, the publicly traded company based at Jade Heart Health.
The company said in its SEC filings that it researches and develops hydrogen- and oxygen-generation technologies. It designs, manufactures and sells machines using that technology for welding, cutting and other industrial uses, the filings say.
Landmark's most recent annual report, for the year ending Jan. 31, 2012, listed $212,233 in sales and a net loss of $510,302 "We have incurred losses since inception, and have not yet received revenues from sales of products or services," the report states.
Despite the losses, the company reported some big-ticket deals. Most notably, in September 2010, it agreed to pay $2.78 million for the assets and patents of a company in China. Payment was made in the form of a promissory note that could be converted into $1 million in Landmark stock.
"Just speculating … but if you have a company with no profits but it's making a $2.78 million deal — that's a red flag," said Martina E. Vandenberg, a Washington D.C.-based lawyer whose Human Trafficking Pro Bono Legal Center helps victims through the criminal justice system and in seeking damages against perpetrators.
Speaking generally about human-trafficking cases, Vandenberg said, "You have all of this cash from an illegal business, and you have to figure out how to get that cash in the regular economy."
Securities lawyers say it's hard to tell from SEC documents alone whether any company is a legitimate entity or a means of laundering money.
In recent years, groups such as Global Financial Integrity have sought to highlight how companies can be used to hide so-called "dirty money" made from crime, making it harder to recover than when it's used to buy property such as homes or cars.
"That's concrete. That's something that authorities can seize," said Josh Simmons, a legal consultant to GFI. "You can send money all over the world; it's extremely difficult to trace."
According to the SEC filings, Landmark began as Reflex Inc., which was incorporated in Nevada in 2007 and described its business as developing, manufacturing, and selling degradable fast-food packaging in Asian countries.