The move came as prosecutors charged Yoo Woo-seong, a 34-year-old defector who previously worked at the Seoul municipal government, with carrying out espionage for Pyongyang's spy agency.
Prosecutors allege that Yoo collected detailed information on some 200 North Korean defectors in the South while he was working at the Seoul city government and relayed it to the North.
After a local district court acquitted Yoo of espionage charges in August 2013, allegations arose that the country's spy agency forged evidence to help the prosecution appeal his innocence.
On Monday, the prosecution team asked the Seoul High Court to allow it to amend the indictment, alleging that Yoo, who held a Chinese passport while living in the communist regime, came to the South by deliberately withholding his nationality.
The prosecutors also handed new evidence to the court, saying that Yoo previously had undergone prosecution questioning on suspicion of earning money by helping other defectors in South Korea send money to their homeland.
Yoo, however, has denied the allegations, saying that he simply helped a fellow businessman. (Yonhap)