The Tokyo District Court acquitted an American couple Thursday who had been charged with fatally injuring their 4-year-old son in their makeshift gym in Shinagawa Ward, Tokyo, in 1994.

Terry Beamon, 52, and his wife, Jewel Curtis, 48, were charged with pounding their son with two wooden rods in October 1994, causing multiple external wounds that triggered fatal traumatic shock. They were arrested in June 2000 and have been in custody since then.

Presiding Judge Masanori Hatoko acknowledged the boy died because of the severe bodily injuries but concluded the evidence did not prove the prosecutor's allegation that the couple conspired to kill their son.

The fatal wounds "could have been made when the victim practiced martial arts with other students" at the gym, the court said, adding it is possible that others, including the boy's brothers, caused the injuries instead of the defendants.

"There is no evidence of a crime," Hatoko said. Beamon, who describes himself as a martial arts grandmaster, nodded as the verdict was read. He and Curtis had argued that their son's death was caused by medical malpractice at the hospital.

Beamon and Curtis came to Japan in 1989 on a 90-day tourist visa and had re-entered the country every three months to avoid deportation.

Although reports suggested the martial arts school was engaged in religious activities in a commune-style environment, the two have denied this claim.

"Mr. Beamon seemed content with the verdict as he shook my hands. His wife also said the ruling was fair and justifiable," Osamu Wakuda, their attorney, told reporters afterward.

However, Wakuda said his clients may face deportation and will be held at an immigration facility because their visas expired during the trial.