A Seoul appellate court on Monday sentenced a former national intelligence chief to three years in prison for violating state intelligence and election laws, going back on a previous ruling that acquitted him of election meddling.
The Seoul High Court ruled that Won Sei-hoon, former director of the National Intelligence Service, interfered in the 2012 presidential election by ordering staff to make political postings online to sway public opinion.
"The agency's cyberactivity interfered in public's decision-making while neglecting its duty to keep political impartiality, which is required by law," the verdict read. "(The NIS) cannot avoid the fundamental criticism that it harmed democracy."
Judges rejected a lower court ruling that found that his orders were not intended to influence the election.
The 64-year-old had been sentenced to two years and six months in jail, suspended for four years, by the lower court last year for charges of violating the law governing the NIS.
Public criticism has since grown over the ruling, which recognised Won's interference in the election but not his support for a particular presidential candidate.
The appeals court said he had directed his staff to post some 270,000 political messages online with 716 Twitter accounts against the opposition-bloc candidate Moon Jae-in.
Won defended himself, claiming that "he worked for the country and public." He was detained immediately after the court's ruling.
Won's attorneys said they would consider appealing against the decision.
After the court made the decision, the ruling Saenuri Party expressed "regrets" over the court's ruling but acknowledged the necessity to "draft up preventive measures against such wrongdoings."
The main opposition New Politics Alliance for Democracy hailed the court's decision, saying that "it is a landmark ruling that proves that constitutionalism is still alive."
Won, a confidant of former President Lee Myung-bak, headed the NIS for about four years until early 2013.
The ex-spy chief served one year and two months in prison until last year for a separate bribery conviction. He was found guilty of having accepted kickbacks from a businessman while in office.
Meanwhile, Kim Yong-pan, a former Seoul police chief who was suspected of soft-pedaling a probe into the high-profile election-meddling scandal, was acquitted by the top court late last month.