LOS ANGELES  - Rights group Amnesty International on Thursday called on California to end the “shocking” conditions inside its prison isolation cells, which house some 3,000 inmates. Prisoners in the cells are confined for at least 22 and a half hours a day in windowless rooms, with no access to work, rehabilitation programs or any group activities, Amnesty said. It added that 78 inmates have spent more than two decades inside the cells. “The conditions and length of imprisonment in California’s isolation units are simply shocking,” Angela Wright, an Amnesty researcher who visited a number of prisons in the state, said in a statement accompanying the report. “To deprive prisoners in a segregated environment of natural light, adequate exercise or meaningful human contact is unnecessarily punitive and unjustifiable in all circumstances.” Prison officials could not immediately be reached for comment. The isolation cells are intended for only the most dangerous prisoners - mainly gang members - but Amnesty said many of the inmates there have mental or behavioural issues, or are being penalized for repeated minor infractions. “We fully recognize the challenges faced by prison administrators in dealing with prison gangs and recognize that it may sometimes be necessary to segregate prisoners for disciplinary or security purposes,” Wright said. “However, current conditions of isolation are extremely severe and too widely used. Segregation should be imposed only in exceptional circumstances and for as short a period as possible.”