Connecticut death row inmates who are suing the state over alleged racial and geographic biases in the state’s death penalty are supporting a plan to hold the trial in a prison instead of a courthouse. Inmates’ lawyers said in a court document filed Friday that the plan by state officials was ‘‘adequate.’’ The plan calls for the trial to be held at Northern Correctional Institution in Somers, which houses death row, beginning in September and to be broadcast via a live video feed to Rockville Superior Court so the public can watch. The trial would be held in one of the prison’s dayrooms, where each inmate and his lawyer would sit together at their own table. Nine of the 10 men on death row are plaintiffs in the appeal. The state repealed capital punishment for all future crimes earlier this year.