The father was killed instantly and seven others were injured in the blast, police in Nikipol said.
The three defendants were among those wounded.
Seven others were injured in the blast, including the three defendants (Police handout)
Pictures from the scene showed blood on the floor of the wrecked courtroom.
In a statement, police said: “Today, on November 30, at 11.20, in the Nikopol court, during a hearing of the case on murder, the victim’s father pulled out two grenades and blew them up.
The grenades caused devastation and blew out the courtroom’s windows (Police handout)
“The man died on the spot from the explosion.
“Three defendants, two convoy officers, a court officer and one civilian were injured.
“All victims were taken to the hospital.”