The top torture investigator in the United Nations wants access to California prisons to determine whether prisoners’ rights are being respected. The official wants to specifically look into the practice of solitary confinement, which sparked a hunger strike over the summer in California jails.

In an interview with the Los Angeles Times editorial board, Juan Mendez, the UN special rapporteur on torture, said that there should be “more justification” for placing inmates in isolation units. Mendez also said that “we should put the burden on the state that this is the proper way to do things, and we should all be a lot more skeptical.”

10,000 inmates are in solitary confinement in California. Advocates for prisoner rights’ say that many inmates are placed in isolation on flimsy evidence of belonging to a gang.

In May, Mendez was asked to investigate solitary confinement in California to determine whether international law is being adhered to. His request has to be cleared by the U.S. State Department and the California governor. While Governor Jerry Brown said that he was unaware of Mendez’s request, the State Department told the LA Times that they are open to coordinating a visit.

Mendez has long been outspoken on the issue. In 2011, he called on nations around the world to ban the practice in most cases, saying that it “can amount to torture or cruel, inhuman or degrading treatment.”