A psychiatrist who examined the teenager arrested over the May 3-4 bus hijacking, in which one person was killed, has told prosecutors he could not determine whether the boy is mentally fit to be held criminally liable, investigative authorities said Wednesday.

The doctor in Hiroshima who recently performed summary psychiatric tests on the 17-year-old at the request of the Hiroshima District Public Prosecutor's Office said he cannot tell if the boy was telling him the truth during the short interviews, according to the prosecutors.

The doctor's analysis may undermine the prosecutors' assertions that the boy, judging from his behavior during the 15-hour ordeal and the consistency of his testimony since his arrest, has at least the minimum mental capacity to understand his criminal responsibility.

Despite the doctor's findings, the prosecutor's office plans to forgo a full analysis of the boy's mental state and send his case to a local family court on June 5 with the recommendation that he be tried in a criminal court.