CAT/OP/KAZ/1/Add.1 special care units or restricted housing, whether as a disciplinary sanction or for the maintenance of order and security, including promulgating policies and procedures governing the use and review of, admission to and release from any form of involuntary separation. 253. National laws and regulations provide for special treatment for prisoners serving life sentences. 254. Moreover, rule 89 of the Nelson Mandela Rules stipulates that the fulfilment of these principles requires individualization of treatment and for this purpose a flexible system of classifying prisoners in groups. It is therefore desirable that such groups should be distributed in separate prisons suitable for the treatment of each group. 255. According to rule 93 of the Mandela Rules, the purposes of classification are: (a) To separate from others those prisoners who, by reason of their criminal records or characters, are likely to exercise a bad influence; (b) To divide the prisoners into classes in order to facilitate their treatment with a view to their social rehabilitation. 256. So far as possible, separate prisons or separate sections of a prison shall be used for the treatment of different classes of prisoners. 257. In addition, preliminary observation 2 of the Nelson Mandela Rules stipulates that, in view of the great variety of legal, social, economic and geographical conditions of the world, it is evident that not all of the rules are capable of application in all places and at all times. They should, however, serve to stimulate a constant endeavour to overcome practical difficulties in the way of their application, in the knowledge that they represent, as a whole, the minimum conditions which are accepted as suitable by the United Nations. 258. For example, even in the United States of America, in a prison that is by no means the strictest in the country, convicted prisoners are moved around in hand and leg shackles. In addition, some convicted prisoners are held in rooms in which they can only stand and only in their underwear. Paragraph 123 The Subcommittee also recommends abolishing the practice of keeping prisoners serving life sentences separate from other prisoners serving long sentences. As with all prisoners, the ultimate aims remain rehabilitation, reinsertion and reintegration. Therefore, contact with the outside world should not be restricted on the basis of the sentence or disciplinary regime. 259. Under article 141 of the Penalties Enforcement Code, prisoners serving life sentences are placed in cells. 260. Educational activities for convicted prisoners are organized with due regard to the requirements of detention in cells. 261. Convicted prisoners are entitled to a daily walk lasting: (1) One hour for those held under the strict regime; (2) One and a half hours for those held under the ordinary regime; (3) Two hours for those held under the relaxed regime. 262. In accordance with article 27 of the Penalties Enforcement Code, it has been made possible for prisoners serving life sentences and those in prison hospitals to receive primary, basic secondary and general secondary education. 263. Convicted prisoners are encouraged to take primary, basic secondary and general secondary education, and their willingness to do so is taken into account in determining their level of conduct and their character assessment. 30 GE.19-01981