The evaluation is due to be released this month, sources said.
But if Matsumoto, founder of Aum Shinrikyo, is deemed mentally unfit, the appeals trial will be suspended.
The evaluation was initiated by the Tokyo High Court in September after Matsumoto’s appeal stalled because defense lawyers claimed their client was unable even to communicate.
In February 2004, the Tokyo District Court sentenced Matsumoto to death on murder and other charges. He was found guilty of masterminding the 1995 sarin attacks on the Tokyo subway system that left 12 dead as well as other crimes by his disciples.
Aum Shinrikyo now calls itself Aleph.
After it reviews the report and hears from the defense team and prosecutors, the high court will decide if Matsumoto is fit to continue his appeal.
If he is found fit, the defense team must give the Tokyo High Court a crucial document it has withheld since August–a summary of its reasons for appealing.
Matsumoto’s attorneys have said they cannot prepare the summary because their client could not communicate with them.
If the defense still refuses to produce that paper, the court could dismiss the appeal.
A dismissal could lead to the death sentence becoming final, although the defense may file an objection.
If the defense team hands in the summary, the hearings will resume, unless the court rejects the paper for missing the August deadline.
In that situation, the case would likely go on to the Supreme Court. But then, Matsumoto’s lawyers would have to change tactics, as the trial would move forward on the premise that Matsumoto is mentally competent.
Presiding Judge Masaru Suda agreed to the psychiatric test in order to move the stalled process forward.
In December 2004, Suda took the rare step of meeting Matsumoto in person. The judge found him capable of understanding him.
The court’s evaluation has been conducted by a court-appointed psychiatrist. The same doctor in a previous case found another defendant, who is now on death row, to be mentally competent.
Because they fear the psychiatrist could decide against them, defense lawyers offered him assessments by other experts in support of their position, sources said.
Detention authorities have reported that Matsumoto recently uttered such phrases as “What are you doing, you fool?” and “Don’t make a fool of me.”