A conclusive presumption (also known as an irrebuttable presumption) is a type of presumption

Presumption

In the law of evidence, a presumption of a particular fact can be made without the aid of proof in some situations. The types of presumption includes a rebuttable discretionary presumption, a rebuttable mandatory presumption, and an irrebuttable or conclusive presumption. The invocation of a...

 used in several legal systems.

England and Wales

In English law

English law

English law is the legal system of England and Wales, and is the basis of common law legal systems used in most Commonwealth countries and the United States except Louisiana...

, a conclusive presumption is a presumption of law that cannot be rebutted

Rebuttal

In law, rebuttal is a form of evidence that is presented to contradict or nullify other evidence that has been presented by an adverse party. By analogy the same term is used in politics and public affairs to refer to the informal process by which statements, designed to refute or negate specific...

 by evidence

Evidence (law)

The law of evidence encompasses the rules and legal principles that govern the proof of facts in a legal proceeding. These rules determine what evidence can be considered by the trier of fact in reaching its decision and, sometimes, the weight that may be given to that evidence...

 and must be taken to be the case whatever the evidence to the contrary.

For example, the doli incapax rule conclusively presumes that a child less than ten years old cannot be held legally responsible for his or her actions, and so cannot be convicted of committing a criminal offence. The age was seven at common law

Common law

Common law is law developed by judges through decisions of courts and similar tribunals rather than through legislative statutes or executive branch action...

, and raised by the Children and Young Persons Act 1933

Children and Young Persons Act 1933

The Children and Young Persons Act 1933 is an Act of the Parliament of the United Kingdom of Great Britain and Northern Ireland...

 to eight (section 50) and by the Children and Young Persons Act 1963 to ten. A similar rebuttable presumption

Rebuttable presumption

Both in common law and in civil law, a rebuttable presumption is an assumption made by a court, one that is taken to be true unless someone comes forward to contest it and prove otherwise. For example, a defendant in a criminal case is presumed innocent until proved guilty...

, that a child between the ages of ten and fourteen was not capable of committing a criminal offence, was abolished by the Crime and Disorder Act 1998

Crime and Disorder Act 1998

The Crime and Disorder Act 1998 is an Act of the Parliament of the United Kingdom. The Act was published on 2 December 1997 and received Royal Assent in July 1998...

. Now the age of criminal responsibility

Defense of infancy

The defense of infancy is a form of defense known as an excuse so that defendants falling within the definition of an "infant" are excluded from criminal liability for their actions, if at the relevant time, they had not reached an age of criminal responsibility...

 in England and Wales

England and Wales

England and Wales is a jurisdiction within the United Kingdom. It consists of England and Wales, two of the four countries of the United Kingdom...

is 10.

The new addition to the Crime and Disorder Act 1998 (c. 37) states

Section 34: Abolition of rebuttable presumption that a child is doli incapax. The rebuttable presumption of criminal law that a child aged 10 or over is incapable of committing an offence is hereby abolished. http://www.socyberty.com/Issues/Doli-Incapax-An-Issue-for-All-to-Discuss.216331

See also the case of R v JTB [2009] UKHL 20. Despite obiter comments in the earlier case of Crown Prosecution Service v P [2007] EWHC 946 (Admin) (27 April 2007), doli incapax as a defence and as a presumption for children aged 10 or above was abolished by section 34 Crime and Disorder Act 1998.