SHANGHAI, July 17 -- A foreign couple accused of illegally obtaining private information on Chinese citizens will be tried in public, Shanghai No.1 Intermediate People's Court announced on Thursday.

The couple, Peter William Humphrey, 58, a British national, and his American wife Yu Ying Zeng, 61, were arrested last August. They had been hired by GlaxoSmithKline (GSK) China's Mark Reilly as private investigators in 2013.

It is the first indictment of foreigners for illegal investigation in China.

Prosecutors have found that the couple illegally trafficked a huge amount of personal information on Chinese citizens to seek profits via a company called ChinaWhys Co. Ltd., registered in 2004 in Shanghai.

The personal information traded by the couple included household registration details, background of family members, real estate, vehicles, call logs and exit-entry records.

Apart from buying information illegally from others, the couple also obtained the information by means such as secret photography and tailing. The couple compiled reports and sold them at high prices to their clients, mostly multinational corporations, including GSK China.

Humphrey told reporters that in April 2013 he was contacted by Mark Reilly, then GSK China's general manager and Zhao Hongyan, its legal department director. He was given an advanced payment of 100,000 yuan (16,143 U.S. dollars). Reilly asked him to find out who disclosed information to Chinese authorities and GSK executives on bribes paid by GSK China.

Humphrey said he only learned the details of the case when he finished a two-month investigation. Before that, Reilly had told him that "the informant was making a groundless accusation".

After the investigation, Humphrey found the bribery claim was probably valid based on his work experience of about a dozen years. He felt he was "betrayed and used" and GSK China's suspicions about the informant were "unfounded". Humphrey also admitted having used illegal means during his investigation.

The two defendants hope their families can attend the trail, said the court.