YOKOSUKA NAVAL BASE, Japan — U.S. Navy Seaman Olatunbosun Ugbogu was charged Thursday with robbery-murder, which could bring the death penalty or life imprisonment in Japan if he’s found guilty.

The indictment contradicts the suspect’s contention that he is mentally ill. The 22-year-old said he killed taxi driver Masaaki Takahashi because of “overpowering voices” in his head, not to get out of paying a $195 fare.

But Ugbogu “stabbed the taxi driver” and “by doing so, he escaped from paying the taxi fare,” a Yokohama District Public Prosecutors Office spokesman said Thursday. Ugbogu also was charged with illegally carrying a knife, the spokesman said.

The 61-year-old driver was found in his taxi in a quiet alley in Yokosuka’s Shioiri neighborhood, with his seat belt fastened and the motor running. In a court statement April 11, Ugbogu said voices, which he describes as “spirit friends,” told him to get into the cab in Tokyo, ride it to Yokosuka and stab Takahashi in the neck.

Ugbogu, a Nigerian citizen, was in deserter status from his command on the Yokosuka-based USS Cowpens at the time of the crime. His credit card was found in the taxi, and he later turned himself in to Navy authorities, who held him at Yokosuka until Japanese authorities arrested him April 3.

Ugbogu’s attorney, Yasutoshi Murakami, had not yet received a copy of the charges Thursday evening and declined to comment on the indictment. He previously had argued against the robbery motive, saying Ugbogu didn’t take any money from the taxi or the driver and had plenty of money with him.

The killing caused an international stir, prompting apology visits to Japanese leaders by the U.S. ambassador to Japan, the commander of the U.S. Navy in Japan and other military officials.

Yokosuka-based Americans underwent a mandated mourning period in the wake of the killing with a curfew and a ban on alcohol sales and consumption. Measures have since eased, but Navy leaders have vowed to continue to work on preventing violence from within their ranks.