74 Human Rights in Counter-Terrorism Investigations The use of lethal force is an extreme measure to which the police should resort only in exceptional situations, when it is strictly unavoidable in order to protect life and less extreme measures are not sufficient. It is generally recognized that the police can use lethal force to protect life in the following circumstances: • self-defence or the defence of any other person against the imminent threat of death or serious injury; • the prevention of the perpetration of a particularly serious crime involving grave threat to life; • the arrest of a person presenting a grave threat to life and resisting their authority; and • the prevention of the escape of such a person.75 The questions that law enforcement officials should always ask themselves when using force are: • Could I achieve my objective by less forceful or violent means? • Is the likely consequence of the force I am using proportionate to the harm I am trying to prevent? • Can I use force without jeopardizing the life of uninvolved people? Any use of force must be prescribed by law, justified, necessary, proportionate and non-discriminatory. Police officers are required to minimize the level of force they apply and to adopt a gradual response, proportionate to the seriousness of the situation they are facing. They should take into consideration the degree of resistance encountered, as well as the legitimate objective to be achieved, such as the arrest and the potential consequences of it not being effected at that time. Even in extreme cases, international human rights standards stipulate that the use of lethal force must be “absolutely necessary’’ to protect life, as is reiterated in the UN Code of Conduct for Law Enforcement Officials, the UN Basic Principles on the Use of Force and Firearms by Law Enforcement Officials and the European Code of Police Ethics.75 75 These circumstances are set down in Principle 9 of the UN Basic Principles on the Use of Force and Firearms by Law Enforcement Officials.