An appellate court on Wednesday gave a lighter sentence of a suspended jail term for Song Du-yul, a Korean-German sociology professor accused of violating the anti-communist security law, saying there is no clear evidence showing he was a member of the North Korean politburo.

The Seoul High Court sentenced Song to three years in jail with the term suspended for five years.

Song was sentenced by a lower court to seven years in jail in March, giving credit to a key charge that he had served as a secret member of the decision-making politburo of the North’s ruling Workers’ Party under the alias of Kim Chul-soo.

``It is difficult to acknowledge the prosecution’s claim (that he is a member of the politburo of the North’s Workers’ Party). It lacks evidence,’’ the Seoul High Court said in its ruling.

Accepting some of the charges that he had worked for North Korea, the court said Song deserves punishment but the sentence should be adjusted.

The court ruling is expected to fuel disputes over Song between conservative and liberal forces and the existence of the anti-communist National Security Law.

Song, 59, a sociology professor at Germany's Muenster University, was taken into custody for violating the security law when he arrived here last year after 37 years in exile due to his relationship with Pyongyang.

The ruling came as the security law, which has been used by previous governments to curb political dissidents and activists, is becoming a hot issue between political circles. Recent polls show more than 80 percent of lawmakers from both ruling and opposition parties recognize the need to revise or scrap the security law.

Earlier this month, political parties traded accusations over a television program that depicted Song as a victim of the law. Critics argue the laws’ vaguely worded clauses have been used arbitrarily by governments to criminalize the exercise of freedom of expression and conscience.

The case has been drawing attention from international human rights groups and German academia.

In May, 48 German political and academic leaders delivered a statement calling for Song’s release to the presidential office of Chong Wa Dae. A group of 175 Korean students studying in Germany filed a petition to the appeal court early in June to ask for his release.