Upholding a lower court ruling, a Seoul appeals court on Friday acquitted a North Korean defector of charges that he carried out espionage activities for Pyongyang.

Yoo Woo-seong, the 34-year-old defector who formerly held a Chinese nationality in the communist regime, was at the center of a high-profile forgery case in which Seoul's main intelligence agency was found to have fabricated Chinese government documents to frame him. 

The Seoul High Court delivered a not-guilty verdict to Yoo, citing the lack of credibility in the testimony of the defendant's younger sister, who had first raised spy charges against him in the trials. 

The court, however, found Yoo guilty of entering the South by hiding his ethnic background, in violation of the passport act and the relevant law governing N. Korean defectors.

 Yoo was sentenced to one year behind bars, suspended for two years, and was ordered to pay a fine of 25.65 million won (US$24,700).

 "The sister was deprived of the basic right to meet her lawyers while undergoing questioning by the National Intelligence Service (NIS)," judge Kim Heung-joon said in his ruling.  

The judge added that the sister, under psychological pressure, provided a false statement after being persuaded by the NIS.

 Yoo was indicted on the charge of collecting detailed information on some 200 defectors in the South while he was working at the Seoul city government and relaying it to the North.

After a Seoul district court acquitted Yoo of espionage in August 2013, prosecutors appealed the verdict and submitted Chinese immigration records on Yoo's visits to the North. But some of the documents were later found to have been forged, and suspicions have since arisen that the NIS was involved in the fabrication.

On April 14, prosecutors announced the results of a two-month investigation into the scandal, concluding that the NIS fabricated the immigration records. But prosecutors said they found no evidence that higher-ranking officials, including NIS chief Nam Jae-joon, were involved. 

Following an apology of NIS director Nam Jae-joon, President Park Geun-hye also issued a public apology and vowed to reform the NIS. (Yonhap)