Usted buscó: 他是在成年人监狱服刑 (Chino (Simplificado) - Inglés)

据称，他是在成年人监狱服刑。
he was is said to be serving his sentence in an adult a prison for adults.

(a) 将命令置于惩诫中心的未成年人置于成人监狱；
(a) that minors ordered to be placed in disciplinary centres are put in adult prisons;