Dzhokhar Tsarnaev’s attorneys argued that conditions the accused Marathon bomber faces in custody are similar to torture and have asked a judge to ease restrictions.

A motion filed today in US District Court in Boston by Tsarnaev’s lawyers claims that he has been left in near-total isolation with the exception of legal visits, the Globe reports. Weather permitting, he is allowed limited time outdoors in an enclosed space on weekends.

His attorneys are claiming that Tsarnaev has been “subjected to extraordinary and severe restrictions”, that have impaired their ability to defend their client, the AP reports.

The United Nations, his attorneys argued, identifies long-term solitary confinement as a form of torture, the Globe reports.

Because his confinement conditions are based on allegations regarding Tsarnaev’s involvement in the Marathon Bombing and the murder of MIT officer Sean Collier three days later, rather than his behavior in custody, attorney’s say that restrictions are “effectively punitive,” the Globe reports.

The 20-year old Tsarnaev could face the death penalty if convicted.