The plaintiffs in the case are inmates at Pelican Bay State Prison near Crescent City, Calif. "In the most severe cases," Juan Mendez says, indefinite solitary confinement — like that practiced at Pelican Bay — "can even be considered torture." Rich Pedroncelli/AP hide caption

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California has agreed to revise its rules on solitary confinement. This file photo shows a cell in the Secure Housing Unit of Pelican Bay State Prison in Crescent City, California. Reuters /Landov hide caption

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Nicklas Trujeque in his solitary confinement cell in New Mexico State Penitentiary. Inmates spend 23 hours a day in these cells, with a one-hour period in an open cell outside. According to the New Mexico ACLU, until recent state reforms, the average length of stay for an inmate here was around three years. Natasha Haverty/For NPR hide caption

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A part of Eastern State Penitentiary in Philadelphia is shown in 2008. The penitentiary opened in 1829, closed in 1971, and then historic preservationists reopened it to the public for tours in 1994. Matt Rourke/AP hide caption

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Latandra Ellington, 36, was serving time for tax fraud at Lowell Correctional Institution when she died. Florida Department of Corrections hide caption

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Daniel Genis, son of Soviet emigre Alexander Genis, served 10 years in prison for armed robbery. He was released last year, and his essays about life in prison have been widely published. Courtesy of Petra Szabo hide caption

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New York Mayor Bill de Blasio tours and meets with youth Dec. 17 at Second Chance Housing on Rikers Island in New York City. Second Chance Housing is an alternative for incarcerated adolescents, instead of punitive segregation, also known as solitary confinement. Susan Watts/Getty Images hide caption

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The Lafayette Parish Correctional Center in downtown Lafayette, La. By most counts, Louisiana has the highest incarceration rate in the country, but sentencing reformers have loosened some of the state's mandatory minimum sentences and made parole slightly easier to get. Denny Culbert for NPR hide caption

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The U.S. holds more prisoners in solitary confinement than any other democratic country, according to critics of the treatment. Here, an immigrant detainee makes a call from his "segregation cell" at a detention facility in Adelanto, Calif., last November. John Moore/Getty Images hide caption

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Brazil's General Superintendency of Prisons of Alagoas (SGAP) released this photo last Dec. 31 of a cat caught with contraband taped to its body at a medium-security prison in Alagoas state. /AP hide caption

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From 2006 to 2010, at least 148 female inmates at two California facilities had tubal ligation surgeries. Some of the surgeries took place at the Valley State Prison for Women, seen here in 2000. Gary Kazanjian/AP hide caption

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