The July 2016 killings at the facility in Sagamihara, southwest of Tokyo, where Uematsu had once worked, shocked the country, as violent crime is rare due to strict gun control
The trial of a man accused of stabbing to death 19 disabled people at a care home in 2016 was interrupted on Wednesday after the man seemed to put something in his mouth, started struggling with court officials and lay on the floor writhing.
Satoshi Uematsu, 29, did not enter a plea before the incident on the first day of the trial. His lawyer said Uematsu had a psychiatric disorder that made him mentally incompetent.
Uematsu is charged with killing 19 disabled people and wounding 26 people in the care centre - one of post-war Japan's worst mass killings.
Japanese media has said Uematsu, who appeared in court wearing a navy blue suit and tie, and with his hair in a long ponytail, had intended to plead not guilty.
But the court session abruptly went into recess after Uematsu made motions as if putting something in this mouth, Japanese media said, and began struggling with officials. A Reuters witness saw him writhing on the floor and being restrained by three uniformed court officials.
Family members of the victims watched from a screened off area of the courtroom.
The July 2016 killings at the facility in Sagamihara, southwest of Tokyo, where Uematsu had once worked, shocked the country, as violent crime is rare due to strict gun control.
Interest in the trial was intense, with nearly 2,000 people lining up in cold rain for 26 viewing seats, and broadcast trucks lined the streets in front of the courthouse.
The violence also sparked debate about the need for change in a society where people with disabilities can still suffer stigma and shame, a situation highlighted by the fact that the families of most of those killed have not revealed their names.
One woman on Wednesday bucked the trend, telling NHK national broadcaster that Uematsu's trial prompted her to change her mind about concealing the name of her daughter, 19 when she was killed.
Photos showed the young woman, who was autistic and unable to speak, smiling shyly as she entered junior high and with short hair in a photo taken by her mother soon after she entered the care home, just months before she was killed.
"She loved music, she lived as energetically as she could," her mother wrote in the statement carried by NHK, saying she last saw her daughter two days before her death.
"Her name was Miho. I want that public as proof that she existed. I want people to know who she was."