CAT/C/GRC/CO/7 35. Under no circumstances should the State party expel, return or extradite a person to another State where there are substantial grounds for believing that he or she would be in danger of being subjected to torture. Moreover, as is indicated in paragraph 20 of the Committee’s general comment No. 4 (2017) on the implementation of article 3 in the context of article 22, diplomatic assurances should not be used as a loophole to undermine the principle of non-refoulement as set out in article 3 of the Convention. The State party should thoroughly consider the merits of each individual case, including the overall situation with regard to torture and illtreatment in the country of return, provide for independent post-return monitoring and compile disaggregated data on extraditions. Conditions of detention 36. While welcoming the efforts made by the State party to reduce prison overcrowding and improve health-care services in prisons, the Committee is concerned that high occupancy rates and poor living conditions remain serious problems in the prison system. It also observes with concern that no concrete measures have been taken to limit the practice of remand in custody. Furthermore, as was acknowledged by the delegation, rules on the separation and categorization of prisoners according to their legal status are still not being implemented, due to the inadequate structure of the prison system. The Committee takes note of the statement made by the State party’s delegation that prisoners serving life sentences are subject to the regular prison regime, but it was not provided with information on whether they can make a request for their sentences to be reviewed, with a view to their reduction. With reference to its previous concluding observations (CAT/C/GRC/CO/5-6, para. 16), the Committee appreciates the information provided by the delegation on the use of electronic metal detectors and drug urine tests to search prisoners, staff and visitors, as alternatives to invasive body searches (arts. 11 and 16). 37. The State party should: (a) Continue its efforts to improve conditions of detention and alleviate the overcrowding of penitentiary institutions, including through the application of noncustodial measures. In that connection, the Committee draws the State party’s attention to the United Nations Standard Minimum Rules for the Treatment of Prisoners (the Nelson Mandela Rules), the United Nations Standard Minimum Rules for Non-custodial Measures (the Tokyo Rules) and the United Nations Rules for the Treatment of Women Prisoners and Non-custodial Measures for Women Offenders (the Bangkok Rules); (b) Ensure, in law and in practice, that pretrial detention is not excessively applied or prolonged; (c) Ensure the strict separation of pretrial detainees from convicted detainees in all detention facilities; (d) Guarantee the periodic review of life sentences with a view to their commutation, and provide the prisoners concerned with rehabilitation programmes to prepare for their social reintegration in the event of parole; (e) Ensure that strip searches are conducted only in exceptional cases, by the least intrusive means possible, by trained staff of the same sex, and with full respect for the dignity of the person. Psychiatric institutions 38. The Committee regrets the lack of appropriate training on and strict criteria for the use of restraints in psychiatric establishments, as observed by the European Committee for the Prevention of Torture and Inhuman or Degrading Treatment or Punishment in paragraphs 35 to 41 of the report on its April 2018 visit to Greece. While taking note of the information provided by the State party on the content of the draft law governing involuntary hospitalization, the Committee, referring further to the report of the European Committee (paras. 42–55), notes with concern the observations that the current procedural safeguards regarding involuntary placement in psychiatric institutions are insufficient. The 9