A Sri Lankan national charged with raping a young South Korean woman nearly two decades ago was acquitted by the top court on Tuesday, in the final twist of a long-drawn-out investigation into the cold case.

The Supreme Court upheld the not-guilty rulings by the lower courts on the 51-year-old foreigner, whose identity has been withheld, citing a lack of evidence.

"It is difficult to believe the veracity of their testimonies in light of objectivity and details of the statements," the top court said in the ruling.

The defendant was indicted in 2013 on charges of robbing and raping an 18-year-old college student, only identified by her last name Chung, in 1998.

The belated indictment came as the DNA of the defendant, who was arrested for soliciting prostitution to a minor, was found to match that left on Chung's underwear. 

Chung was found dead on Oct. 17, 1998, after being hit by a 25-ton dump truck on a highway in Daegu, some 302 kilometers southeast of Seoul. The police had suspected rape as they found her lingerie 30 meters away from the site of the accident, but concluded it was an accidental death.

In the fresh investigation, the prosecutors found that Chung jumped into the road as she ran away from her attackers in fear and had lost sense of direction in the dark.

The prosecutors indicted the Sri Lankan and two other accomplices of the same nationality on counts of special robbery and rape in 2013. It was about the only criminal charge they could lay against them since the statutes of limitation for rape and special rape in Korea are set at five years and 10 years, respectively.

The lower court and appeals court found the defendant not guilty, saying that the evidence was insufficient to prove the charges.

The prosecution managed to call a witness to the stand who testified that the defendant had told him in person about committing the rape. But the appeals court dismissed the testimony citing a lack of credibility.

The Sri Lankan will be extradited to his country as South Korea is bound by law to send back a foreign criminal who's been given a suspended sentence. He was convicted of sexually harassing a woman in 2013 and driving without a license a few years before that.

The two other accomplices in Chung's case were expelled from the country in the early 2000s due to the illegal stay.

(Yonhap)