98 Resource book on the use of force and firearms in law enforcement longer a need to use (potentially) lethal force. Officers should be able to adjust their assessment of the situation, scaling up and down depending on how the circumstances of the incident develop. They should be able to justify each single shot fired. Factors that must be taken into account when assessing the likelihood that the force may lead to death may include, for example, the kind of firearms used; the likelihood that the law enforcement officer will be able to hit non-essential body parts; the availability of effective medical emergency response and health care; and the presence of other persons who may be affected (and even potentially killed) by the use of force.219 In line with BPUFF principle 10, before firing a shot, the law enforcement officials should identify themselves as such and give a clear warning of their intent to use a firearm, with sufficient time for the warning to be observed, unless doing so would unduly place the law enforcement official at risk or would create a risk of death or serious harm to other persons, or would clearly be inappropriate or pointless in the circumstances of the incident. For example, a warning is clearly futile when the target is already firing. Warning shots should be avoided as they carry serious risk of causing damage or injury. Indeed, it is good practice to prohibit warning shots altogether.220 Shooting at moving vehicles should be avoided, unless it poses an imminent risk of death or serious harm to the official or other persons, as this is also extremely dangerous. Where possible, when law enforcement officials are routinely armed with a firearm, it is desirable that they be issued with their own force-owned weapon and train with that particular weapon for accountability. This way they are responsible for its care, cleaning and can familiarize themselves with the subtleties and nuances of that particular weapon, which can be adjusted to the needs of the “owner” to achieve better accuracy. It also allows easy record-keeping and tracing. Note that all weapons should be stored at the armoury after use and should be registered with every use. A firearm that is not maintained properly can discharge or jam accidentally, potentially leading to serious injuries and sometimes loss of life. Care should be taken to maintain weapons in proper state, typically the responsibility of an armourer. Accidental discharge is almost always due to operator error, carelessness or failure to follow procedure, such as when a law enforcement official drops a gun or accidentally pulls the trigger. Whenever a law enforcement official explains that a death or injury has occurred as the result of a malfunction or accidental discharge, this should be subject of an investigation. The basic principle of accountability is that it must be possible to trace who fired a gun. Hence, modifying or disassembling weapons should not be permitted, as it makes it more difficult to trace who fired the weapon. Also, the trigger of a firearm should require a certain pressure in order to fire, usually indicated in weight, and thus should not be modified. Unauthorized modifications should also be prohibited as they could facilitate careless handling of the instrument. 219  See OHCHR, Human Rights and Law Enforcement, A Manual on Human Rights Training for Law Enforcement Officials, 2017, chapter 5 (Human Rights and Use of Force). 220  When firing a shot in the air, the bullet will come down with a trajectory that cannot be controlled. When firing a shot elsewhere, there is high risk of the bullet ricocheting. In both cases the risk of causing injury or worse to random bystanders is high. In addition, a warning shot could also be perceived as an escalation of the situation rather than an attempt at de-escalation.