He has not had human contact or a good night’s sleep in nearly three decades. Every single day, he wakes to the sound of metal doors clanging open and a pair of disembodied hands pushing a tray of food through a slot into his 64-square-foot cell.

For the next 23 hours, he will stare at the same four walls. If he is lucky, he’ll be escorted, shackled at his ankles and wrists, into a “yard” – an enclosure only slightly larger than his cell – for an hour of solitary exercise.

This is how Russell “Maroon” Shoatz, a prisoner in the restricted housing unit at the State Correctional Institute (SCI) Frackville in northern Pennsylvania, has spent the past 22 consecutive years.

On Thursday, Shoatz’s lawyers submitted a communication to Juan E. Mendez, the United Nations’ special rapporteur on torture and other cruel, inhuman and degrading treatment or punishment, urging him to inquire into why a “father, grandfather and great grandfather” is being held in extreme isolation despite having a near-perfect disciplinary record for over 20 years.

The appeal comes on the heels of a surge in public debate on the practice of solitary confinement in the United States, where on any given day an estimated 81,000 men, women and children are held in some form of “restricted housing” unit, according to Federal Bureau of Justice statistics.

Authorities in each state have a myriad of euphemisms for the practice: administrative segregation, secure housing units (SHUs), “supermax” facilities, protective custody. Whatever the language, critics say the basic conditions remain the same: extreme isolation and sensory deprivation for years at a time.

According to a 2012 report by Human Rights Watch (HRW), the restrictions imposed in “maximum security” facilities often “exceed the fathomable. In Pennsylvania’s most restrictive units, for example, prisoners have all the usual supermax deprivations plus some that seem gratuitously cruel: they are not permitted to have photographs of family members or newspapers and magazines.”

Mendez has already affirmed that holding a human being in isolation for a period exceeding 15 days constitutes a violation of the U.N. Convention Against Torture (CAT).

Back in 2011, his office called for a complete global ban on the use of solitary confinement “except in the most extreme circumstances and for as short a time as possible”, citing numerous studies – some dating back decades, others as recent as Amnesty International’s 2012 report ‘The Edge of Endurance’ – that have documented the long-lasting psychological impacts resulting from even a few days of social separation.