ATLANTA (AP) — An expert report says Georgia's most restrictive solitary confinement facility deprives prisoners of basic human needs and risks causing psychological harm.

The report by psychology professor Craig Haney was filed in federal court as part of a challenge to the conditions in the Special Management Unit of the Georgia Diagnostic and Classification Prison in Jackson. A redacted version of the report was filed publicly Tuesday.

Haney has toured maximum-security prisons in roughly two dozen states and writes that the unit is "one of the harshest and most draconian" he has seen.

Lawyers for current and former prisoners in the unit are asking a judge to order prison officials to improve conditions immediately.

The state has said in court filings that the prisoners haven't been deprived of any rights protected by state or federal law.