Does grabbing someone by the jacket constitute assault?

Question

What is considered assault in England ? An example Person A swore at Person B and was grabbed by the jacket by person B in a casino.

Has Person B committed assault even though person A may have verbally offended person B?

Answer 1

Has Person B committed assault even though person A may have verbally offended person B?

Yes

An assault is any act (and not mere omission to act) by which a person intentionally or recklessly causes another to suffer or apprehend immediate unlawful violence.

The term assault is often used to include a battery, which is committed by the intentional or reckless application of unlawful force to another person.

source

Under common law, the use of force against another must be proportionate and justified, but not excessive in the particular circumstances - Person B's retaliatory assault (and battery) does not appear, according to the details in the OP, to meet this criteria. See palmer v R (19711) AC 814:

It is both good law and good sense that a man who is attacked may defend himself. It is both good law and good sense that he may do, but may only do, what is reasonably necessary. But everything will depend upon the particular facts and circumstances.

Answer 2

First of all, the jurisdiction would be England and Wales. The UK Government has a helpful page on the topic of assault in criminal law, but we are looking for the most basic idea of assault, and I find the sentencing council differentiates it better, and I will quote them from here on, unless otherwise noted.

Common assault (section 39, Criminal Justice Act 1988)

A person is guilty of common assault if they either inflict violence on another person – however slight this might be – or make that person think they are about to be attacked.

Bob committed common assault of Adam for he did inflict violence on Adam. In the alternative, even if Bob misses or not pull through, he made Adam think he was about to be attacked. However, note that common assault becomes battery the moment you actually do damage:

The term assault is often used to include a battery, which is committed by the intentional or reckless application of unlawful force to another person. [...] Assault, as distinct from battery, can be committed by an act indicating an intention to use unlawful violence against the person of another – for example, an aimed punch that fails to connect. https://www.cps.gov.uk/

Assault occasioning actual bodily harm (section 47, Offences against the person act 1861)

For this offence, the assault (which can be intentional or reckless as above) must have caused some physical harm to the victim. It does not need to be serious or permanent but must be more than trifling or transient. Some psychiatric harm can also be covered by this offence, but must be more than just fear or anxiety.

In case Adam ends with a blue eye or more than scratches, Bob can be charged under this section.

Unlawful wounding or inflicting grievous bodily harm (section 20, Offences against the person act 1861)

Grievous bodily harm means really serious physical harm although it does not have to be permanent or dangerous.

If Bob breaks Adam's arm, it's this section that is applicable.

Causing grievous bodily harm with intent to do grievous bodily harm/Wounding with intent to do grievous bodily harm (section 18, Offences against the person act 1861)

Once the assault goes beyond just serious and goes into dangerous, the standard of section 18 is to be applied - this is pretty much one tiny step away from attempted manslaughter or murder!

Answer 3

Yes, but...

Whilst this may well fulfill the requirement of violence (see @RockApe's answer), a further question is "was this lawful?"

Simply responding to a verbal insult by escalating to grabbing clothing is not normally justifiable. However if person B sees this (whether correctly or not) as being the preliminary step to being assaulted by person A, it is entirely lawful for them to take any reasonable steps in self-defence. Grabbing clothing without causing harm to person A is almost certainly reasonable in that situation.

Further to that, if person B is a member of the venue's security staff, they have a duty of care to everyone in the venue. If they consider that person A represents a threat to the safety of other people in the venue, regardless of whether person A has actually carried out any physical actions yet, it is entirely lawful for them to take any reasonable steps to ensure the safety of people in the venue and eject person A. Grabbing clothing may well be reasonable here too, especially if person A was trying to walk off.

Beyond this too, if it gets as far as the police being involved, then we have the concept of the CPS deciding whether a prosecution is "in the public interest". If person A was a prominent politician or a member of the royal family, then perhaps person B manhandling them would be seen as serious enough for the CPS pursue a prosecution. If they are merely a regular member of the public though, and if they suffer no injury or loss, then it is very unlikely that the CPS would take any action, even if person A does press charges against person B.

And then it needs a magistrate to decide whether there should be any penalty against person B; or (if escalated past the magistrate's court) it needs a jury to find them guilty and a judge to decide any penalty. If there was no harm to person A, it's reasonably likely that this wouldn't get traction which is why the CPS probably wouldn't pursue it.