to research the law before they act. If they fail to do so, they can hardly complain if their acts prove unlawful, no matter how transient they may be within the jurisdiction. The only exception to this rule excuses those of reduced capacity, whether as infants or through mental illness (for example, see the principle of doli incapax which raises an irrebuttable presumption in criminal law that an infant is incapable of committing a crime). Sanctity of life Underpinning most social, moral and religious systems is the policy of sanctity of life (also culture of life). In English criminal law, for example, duress is not allowed as a defence to murder because no threat is supposed to overcome a person's moral aversion to taking the life of another. Lord Jauncy in R v Gotts [1992] 2 AC 412 stated: In refusal of treatment and euthanasia, commission and omission by doctors and hospital authorities resulting in the death of patients has become of increasing significance as societies debate whether the duty to preserve life outweighs the right of the autonomous patient to choose death. More contentious are those situations in which the patient is unable to make the choice personally, e.g. because in a persistent vegetative state or en ventre sa mere, i.e. a child in the womb. Doctrine of evasion Similarly, in many branches of law, the doctrine of evasion prevents persons, both natural and artificial, from evading the application of obligations and liabilities already attaching to them. This represents a practical application of the policy that, as an outcome of the social contract, all persons owing allegiance to a state should be entitled to assume that everyone will receive fair and equal treatment before the law, i.e. there will be no favouritism or preferential treatment to any person by virtue of their rank or status within society. As such, this is an exception to the policy in the law of contract which usually allows the parties autonomy to enter into whatever agreement they want and which might otherwise be taken to permit the parties to exclude the normal operation of the law as between themselves (see the policy of freedom of contract). Children There are policies specific to all the main branches of law. Hence, one of the policies in family law is parens patriae, i.e. that the state is the default parent for all those children within its