Reasonable Use of Force, What you Can and Cannot Do

Security work can be a tough job. In addition to long hours on their feet and prolonged exposure to the elements, security workers often find themselves the targets of angry outbursts, various kinds of abuse and even outright assault.

In such cases, self defence is not only necessary to preserve the safety of the security officer themself, but also that of any patrons, customers or members of the public that happen to be in the vicinity.

Accordingly, UK law allows for the application of ‘reasonable force’ at times when the individual (or those nearby) comes under threat. However, the definition the criminal law applies is loose and somewhat open to interpretation.

In this piece, we will attempt to simplify and better explain the definitions of ‘reasonable force’ and ‘excessive’ force, as well as self defence and when the use of force is and isn’t appropriate.

How is ‘Reasonable Force’ Defined?

Essentially, the term ‘reasonable force’ describes the amount of force necessary to protect yourself or your property from unlawful aggression, self defence or harm. Reasonable force is always proportional to the threat presented at the time and must never exceed this, lest it be termed ‘excessive force’.

There is no specific definition of what does or does not constitute reasonable force. This is because UK law understands that each situation is different. If an armed intruder enters a person’s home, for example, it would be considered reasonable for the tenant wishing to defend him or herself to also arm themselves with some sort of weapon. Using a weapon against an aggressive, but unarmed, person on the other hand, would likely be seen as excessive.

However, these definitions are open to interpretation interpretation to any reasonable person, which can cause confusion.

The two main times wherein reasonable force is acceptable are:

  1. a)   in the ‘heat of the moment’ – i.e., as a violent incident is occurring or feels about to occur,


  1. b)   if the perpetrator of a crime is attempting to flee the scene and needs to be tackled and/or restrained.

Citing the necessary use of reasonable force during criminal trials or suits alleging tortious conduct is often a solid defensive tactic and can be backed up by the use of CCTV or Body Camera footage. 

However, that the amount of force used was reasonable within the confines of the law must be proven and determined beyond any reasonable doubt, only a reasonable action can be proven as reasonable force.

Remember, any force used by a person must be proportional to the threat that person believes him or herself to be facing at the time the force is applied.

Understanding Reasonable Force

If a person can prove that the amount of force used was equal to the threat faced by them at the time, they are unlikely to have breached the boundaries of lawful conduct.

Any person in the UK has the right to defend him or herself from harm, as well as to defend others. Fighting back in self defence is generally acceptable, as is tackling and restraining a person who is engaged in criminal behaviour. Beyond that, the definition of reasonable force generally escalates as the threat level does.

The law also recognises the effect offight or flightresponse (also known as hyperarousal or acute stress response) in stressful situations. Section 76(7) (a) of the Criminal Justice and Immigration Act 2008 reads:

“A person acting for a legitimate purpose may not be able to weigh to a nicety the exact measure of any necessary action; and (b) …evidence of a person’s having done what the person honestly and instinctively thought was necessary for a legitimate purpose constitutes strong evidence that only reasonable action was taken…”

Lapses in judgement in such situations are natural – and expected. The person being threatened may overestimate the actual level of the threat. To a certain extent, the law will still attest that they have acted reasonably or in self defence in these cases.

However, it is not considered an act of reasonable force if a person continues to attack the other person after the threat they present has been neutralised or unable to protect oneself (for instance, continuing to hit a person after they’ve given up fighting or chasing a fleeing person down and violently attacking them). 

It is also illegal to pre-plan a trap for someone (for example, inviting a person to visit before treating them like a hostile intruder).

In cases where assault, battery or extreme force has been alleged, courts will be encouraged to consider two key questions regarding the incident.

1)   Did the person using force honestly feel that it was necessary to do so?

2)   Was the force used proportionate to the threat they faced at the time?

If the answer to both questions is ‘yes’, then the force used was reasonable in the eyes of the law. Accordingly, if you ever find yourself considering the use of force, it is always worth mentally asking yourself both questions before proceeding.

Legal force may be used to protect ourselves or others from imminent danger,, prevent crime or assault, to search someone, defend a property or when arresting/assisting in the lawful arrest of criminals.

Security guards may use limited force to escort uncooperative trespassers from the areas they are guarding, but may not harm these trespassers in anything other than self defence or defence of others extreme force.

Compliance (no resistance)Sex/age/size/strengthDoor supervisor presence (observing, passive control)
Verbal resistance (refusing to co-operate, swearing, threatening)Skills/knowledgeTactical communications (verbal and non-verbal)
Passive resistance (refusing to move/leave)Alcohol/drugs/mental impairmentPrimary control skills (carrying out, low level of force)
Active resistance (pulling or pushing away, struggling)Injury/exhaustion/disadvantageSecondary control skills (increase in force, arm-locks and holds etc)
Assaultive/aggressive resistance (fighting, punching, kicking)Numbers/weapons/dangerDefensive tactics (blocks, strikes and takedowns)
Serious/life threatening resistance (armed or serious attack, risk of serious harm or death)Serious imminent dangerSerious or deadly use of force (action likely to or could cause serious harm or even death)

When can Reasonable Force be Used?

Reasonable force may be used in instances of violence or crime, usually in cases where it is necessary to defend oneself or others who may be vulnerable to attack.

Reasonable force may also be used preemptively, in order to stop an attack from happening. If, for example, a person is clenching or raising their fists and appears to be about to strike another person, that person does not need to wait to be attacked for self defence and restraining (not hitting) the would-be attacker and preventing the assault.

Issues that will likely be considered in incidents of self defence include the person’s height, weight or build compared with that of the attacker (a bodybuilder claiming self defense against an old lady by restraining her is not going to hold up in court, for example). 

It will also be asked whether there was a need for such force at all, when the person ceased using force and whether or not force was used with malicious intent.

These considerations form many of the legal boundaries which separate the definition of reasonable force to that of excessive.

When Does Reasonable Force Become Excessive Force?

Once a person is no longer under threat, they cannot claim to be using reasonable force. Typically, when a person goes from self defence to offensive in situations where the threat has diminished or passed, they will be engaged in the act of using excessive force, This is a crime under the criminal law act.

Reasonable force is always proportionate and is generally acceptable. Excessive force is disproportionate and is never acceptable.

Beating a person who is already incapacitated, or unconscious is an act of excessive force (or possibly a case of ‘grossly disproportionate force’), as is chasing a fleeing person down and beating them rather than simply apprehending them.

In less extreme cases, excessive force may include restraining a person who isn’t complying with verbal commands or even issuing verbal threats against a person acting aggressive.

Essentially, engaging in violence outside of self defence, or the use of force that is grossly disproportionate to the force that may be required is using excessive force. The same is true for calculated acts of malice or revenge.

As discussed above, the legal definition of reasonable force is not particularly thorough. The law also encompasses an understanding that extreme or difficult situations can cause people to behave less rationally than normal. 

As a result, there exists some room for discussion, debate and doubt. If a level of force just above that which is needed is used through self defence, it is unlikely that a prosecution will be carried out.

Additionally, because the definition of reasonable force basically increases along with the threat, reasonable force may even extend to the death of the assailant, so long as the assailant was offering an equal amount of violence and the measures used were a) the only option available and b) the last resort. In most cases, such deaths are accidental and can be ruled as acts of self defence rather than manslaughter or murder.

The definition of reasonable force is necessarily vague. This means that the definition of excessive force, though more substantial, still depends on that first definition and, as such, can be misinterpreted and misunderstood. We hope that by presenting this guide, we’ve made things a little bit clearer and easier to understand.

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