There are generally tests that can serve as a guide to what cruel and unusual punishment is according to various legal textbooks in accordance with the law. These are:
- the frequency at which the punishment occurs in society,
- overall acceptance in society,
- severity (the punishment fits the crime), and
- if the punishment is arbitrary.
These exact words were first used in the English Bill of Rights 1689 and later were also adopted in the United States by the Eighth Amendment to the United States Constitution (ratified 1791) and in the British Leeward Islands' Slavery Amelioration Act (1798). Very similar words, "No one shall be subjected to torture or to cruel, inhuman or degrading treatment or punishment", appear in Article 5 of the Universal Declaration of Human Rights adopted by the United Nations General Assembly on December 10, 1948. The right under a different formulation is also found in Article 3 of the European Convention on Human Rights (1950) and in Article 7 of the International Covenant on Civil and Political Rights (1966). The Canadian Charter of Rights and Freedoms (1982) also contains this fundamental right in section 12 and it is to be found in Article 4 (quoting the European Convention verbatim) of the Charter of Fundamental Rights of the European Union (2000). It is also found in Article 16 of the Convention against Torture and other Cruel, Inhuman or Degrading Treatment or Punishment (1984), and in Article 40 of the Constitution of Poland (1997). The Constitution of the Marshall Islands, in the sixth section of its Bill of Rights (Article 2), prohibits "cruel and unusual punishment", which it defines as: the death penalty; torture; "inhuman and degrading treatment"; and "excessive fines or deprivations".
The Eighth Amendment to the United States Constitution states that "cruel and unusual punishments [shall not be] inflicted." The general principles the United States Supreme Court relied on to decide whether or not a particular punishment was cruel and unusual were determined by Justice William Brennan. In Furman v. Georgia, 408 U.S. 238 (1972), Justice Brennan wrote, "There are, then, four principles by which we may determine whether a particular punishment is 'cruel and unusual'."
And he added: "The function of these principles, after all, is simply to provide means by which a court can determine whether a challenged punishment comports with human dignity. They are, therefore, interrelated, and, in most cases, it will be their convergence that will justify the conclusion that a punishment is "cruel and unusual." The test, then, will ordinarily be a cumulative one: if a punishment is unusually severe, if there is a strong probability that it is inflicted arbitrarily, if it is substantially rejected by contemporary society, and if there is no reason to believe that it serves any penal purpose more effectively than some less severe punishment, then the continued infliction of that punishment violates the command of the Clause that the State may not inflict inhuman and uncivilized punishments upon those convicted of crimes."
Continuing, he wrote that he expected that no state would pass a law obviously violating any one of these principles, so court decisions regarding the Eighth Amendment would involve a "cumulative" analysis of the implication of each of the four principles. In this way the United States Supreme Court "set the standard that a punishment would be cruel and unusual [,if] it was too severe for the crime, [if] it was arbitrary, if it offended society's sense of justice, or if it was not more effective than a less severe penalty."
There is great discussion as to whether capital punishment is cruel and unusual. Common arguments are that capital punishment is more expensive when factoring in appeals versus life in prison, and that the government has been wrong before on death penalty cases (therefore, the government could be wrong again, and the government ought not have the authority to end a life). These two arguments alone may or may not qualify under the tests the government puts forth, which could also be considered arbitrary itself, especially if society is not informed enough on these considerable facts. For most of recorded history, capital punishments were often deliberately painful. Severe historical penalties include the breaking wheel, boiling to death, flaying, disembowelment, crucifixion, impalement, crushing, stoning, execution by burning, dismemberment, sawing, scaphism, or necklacing.
In 2008, Michael Portillo on the show Horizon argued that in ensuring an execution is not of a cruel and unusual nature, the following criteria must be met:
The show argued that hypoxia appears to meet the criteria, by way of applying a combination of the gases argon and nitrogen, as the person being executed would not feel any physical pain but would experience a euphoric state. It was further argued that these gases could be applied cheaply and efficiently by restraining the prisoner by way of physical restraints and mask.