The Tokyo District Court on Friday dismissed an indictment against one of the suspected pirates charged with attacking a Japanese tanker off the coast of Somalia in March because the defendant may be a minor.

The defendant testified Friday that he is under 20 years old, and no evidence could be found to prove otherwise. The Tokyo District Prosecutor's Office is expected to send his case to the Tokyo Family Court.

The defendant and three others — of whom one was earlier judged to be a minor — were arrested after allegedly attacking the Guanabara, a Mitsui O.S.K. Lines tanker registered in the Bahamas and operated by a non-Japanese crew, on March 5.

None of the 24 crew members was injured, and the four suspects, who all say they are Somali, were captured by U.S. naval units the following day and transferred to Japan to face trial.

The case involving the defendant earlier determined to be a minor was sent to the Tokyo Family Court, but he was later indicted under the antipiracy law all the same. The suspect judged Friday to be a minor could face the same fate.

Prosecutors said that during investigation the defendant claimed he was "around 21 years old," and was born "around 1990."

At the trial, however, he said he was born Dec. 22, 1991, citing information from his mother and uncle, making him 19 years old.

He explained that prosecutors previously only asked for his rough age and he gave an estimate based on Somalia's traditional calendar, which counts years according to rainy seasons. Two interpreters assisted the court proceedings.

The court said that obtaining objective information regarding the defendant is difficult as Somalia effectively has no central government, and the defendant should undergo routine procedures based on juvenile law.