Judge Anwar al-Enezi ordered formation of a three-member committee of forensic experts to probe the torture claims.
Kuwait had accused four Iranians and three others of forming a ring to spy on the Kuwaiti Army and US troops stationed in Kuwait on behalf of the Pasdaran.
A lower court sentenced two Iranians and a Kuwaiti to death, a Syrian and a stateless man to life in prison while acquitting the two other Iranians, one of whom is the daughter of one of the Iranians sentenced to die and the wife of the Kuwaiti sentenced to die.
At their trial in March, they told the court their confessions had been extracted under torture.
The case has significantly increased tensions between the two countries.
