The case against Nissan Motor Co.'s former Chairman Carlos Ghosn has recently put Japan's controversial criminal justice and detention system in the spotlight, provoking calls for an overhaul of procedures that keep suspects in detention longer if they continue to deny allegations made against them.

Ghosn spent over four months at the Tokyo Detention House across two stints in the facility, until his second release on bail in late April. On Monday, supervisors at the facility disclosed to the media the realities of life behind bars and rejected criticism of its austere form of confinement. Officials declined to comment on specific cases, including that of Ghosn's.

With a total floor space of 154,671 square meters, the prison in Katsushika Ward, Tokyo, currently houses 1,758 inmates, 1,216 of whom are still awaiting trial, according to the officials who spoke to reporters during a tour. The facility is said to accommodate up to 3,010 inmates. A 7.5-square-meter solitary cell shown to The Japan Times and described as typical was tatami-floored and equipped with a short-legged table, a Japanese-style bedding set, a bookshelf, a sink and a toilet bowl by the window. A wooden partition offers some privacy for inmates who prefer to cover the bottom part of their body while using the toilet.