Acts & Omissions
Offences
Criminal offences are either recognised at common law or subsist by statute. The elements of the offence will be defined in common law rules or defined by the terms of the statute.
Some crimes are categorised in terms of the outcome rather than conduct. Murder and dangerous driving are examples.
Conduct that is equally morally blameworthy would not constitute an offence at all if the result of the offence does not occur. In the case of many regulatory offences which are designed to uphold statutory schemes, liability does not depend on fault.
Criminal Act / Actus Reus
Generally, there is a physical manifestation aspect of the offence. In the case of the more serious crimes, there is usually a defined element of fault.
The external or physical aspect of the offence is described as the actus reus or guilty act. Where there is both a guilty act and the required degree of fault (guilty mind/mens rea) then both elements will need to be proved beyond a reasonable doubt. Where an act only constitutes the offence, then this element only is required to be proved beyond reasonable doubt.
The required physical manifestation of the act will depend on the particular offence. It will typically comprise a physical act voluntarily or wilfully done. It may comprise words such as in the case of incitement or procurement of offences. It may be comprised in possession of certain things (e.g. drugs, firearms et cetera
The offence may be constituted by a particular state of affairs. This may be the case where a statute provides that it is the responsibility of particular persons to procure particular outcomes that result in a state of affairs. This may apply, for example, to requirements for health safety and welfare at work.
Voluntary Act
Almost always, the act or conduct concerned must be voluntary. This does not mean that it must be intentional, reckless, or careless.
An involuntary act may occur, for example, if somebody is physically overpowered or controlled by another. This might happen in cases where certain types of press pass or an offence person might be pushed onto the property concerned.
Voluntariness raises issues of automatism, duress, and insanity, which are discussed separately. Duress may be a defence. In some circumstances, insanity may lead to a finding that there is no criminal responsibility. See the separate chapters in that regard.
Automatism
Automatism/involuntary acts would arise only in the most extreme circumstances. For example, a person may have a stroke or epileptic fit without his fault, such as to lose consciousness. In some such cases, there may still be a fault in exposing oneself to the circumstances concerned.
Automatism refers to circumstances where the thing is done by the body without any control whatsoever by the mind. Self-induced automatism may not suffice. For example, a person taking unlawful drugs will not be excused the consequence of what he does.
Omissions
In the case of offences, particularly regularly occurring offences and offences where responsibilities arise, there may be liability for an omission. This may happen, for example, where there has been a failure to do things required by law. There are many examples, including under the Road Traffic Act (licence insurance) and Tax legislation (obligation to return).
A common law offence may arise where there is a specific duty to act and failure to do so. The circumstances are relatively narrow. One example is where a person has a prior responsibility for another. Both at common law and by statute, parents and others in their place have significant duties to children to preserve their lives and protect them from danger.
Traditionally, a person could be liable civilly and criminally if he voluntarily undertook something and failed to reach the relevant standard. Good Samaritan legislation has sought to minimise the perverse effects that may arise.
Prior Responsibility
A person may for example take care and responsibility for an elderly or vulnerable person. In some such circumstances, there may be a duty of care and consequent civil and criminal liability may arise for failure to discharge the duty.
The duty will last for so long the responsibility is assumed the responsibility cannot be abandoned but may cease provided the person is not left in vulnerable circumstances. For example a person was undertaken to care for another may properly divest himself of the duty where it is passed to another responsible person or authority.
Persons may have responsibilities due to their office or employment. A police officer has a range of duties and responsibilities. This may include the duty to intervene where members of the public are endangered and can be readily assisted.
An employer may have responsibility in relation to a matters of public safety. Where  duties are not discharged he may be liable criminally, For example a person employed as a gatekeeper who failed to close gates which were his responsibility might be found liable for manslaughter by reason of gross negligence.
Doctors have duties to preserve life. In some circumstances, failures to perform their duties may be grossly negligent, such as to entail criminal liability.
Difficult questions arise in relation to assisting people who do not wish to be assisted  Generally when a mentally capable person refuses treatment this must be respected.
Where a person refuses life-saving treatment, questions may arise as to their capacity. The former was the court legislation or the modern assisted this session this is position assistance statement may be applied. The person, such as a court or body, makes the relevant decision.