-28 Only if these conditions are fulfilled can staff be in a position to recognise a threat to security at a very early stage and take timely action to prevent it. The term ‘safety’, on the other hand, is linked to the obligation to protect against the risks that prisoners may pose to themselves in terms of selfharm, to other prisoners as well as to prison staff and other persons working in or visiting the prison.30 Ensuring security and safety is of outmost importance, but must be done in the full respect of the dignity and fundamental rights of the persons concerned. To this extent, all measures aiming at ensuring security and safety in prison that interfere with human rights need to respect the following principles: • Legality: All restrictive measures imposed upon a prisoner should be in accordance with international and national law, and have a legitimate objective. • Necessity: The measures must be necessary, i.e. it should be clear that using less restrictive means would not fulfil the objective of ensuring safety and security. • Proportionality: The restrictive measure should be proportional to the risk posed, with an appropriate balance between the protection of the fundamental rights of the prisoner and the State’s lawful interference in the exercise of these rights. Such interference should be the least intrusive possible to fulfil the aim of ensuring security and order in prison and be imposed for the shortest possible duration. • Accountability: The decision-making process should be transparent and records should be kept of the assessment justifying the need for the restrictions imposed. • Non-discrimination: Decisions should be objective and impartial, taking into account only the relevant factors. There should be no discrimination against certain groups of prisoners based on race, colour, religion, ethnicity, nationality, gender, gender identity, sexual orientation, political views or any other factor.31 30. A definition of the term ‘security’ can be found in the EPR, Rule 52.1. 31. See CoE, Protection; see CPT, ‘Solitary Confinement of Prisoners: Extract from the 21st General Report of the CPT Published in 2011’ (2011) CPT/Inf(2011)28-part2, § 55; CoE, CM, ‘Explanatory Memorandum to Recommendation CM/Rec (2014) 3 of the Committee of Ministers to Member States Concerning Dangerous Prisoners’, §§ 52-54.