Excessive bail shall not be required, nor excessive fines imposed, nor cruel and unusual punishments inflicted. Notes for this amendment: Proposed 9/25/1789 - Ratified 12/15/1791
“This amendment prohibits excessive fines and bail, as well as cruel and unusual punishments. The phrase “cruel and unusual punishments” first appeared in the English Bill of Rights. In colonial America, the British often employed branding, whipping, public humiliation and extremely long prison sentences for minor offenses. The Founders believed that justice requires that even those people found guilty of crimes be protected from this kind of treatment.
James Wilson lectured on justice and punishments, saying in 1791, “A nation [that tolerates] cruel punishments becomes dastardly and contemptible. For in nations, as well as individuals, cruelty is always attended by cowardice.” He argued that punishments should be swift, certain, and moderate in order to be effective and prevent further crime. Landmark Supreme Court cases concerning the Eighth Amendment include Gregg v. Georgia (1976)”.
The Gregg case decided that the death penalty was not cruel and unusual punishment under the Eight Amendment of the Constitution as long as it was used “judiciously and carefully” and met “contemporary standards of society, served as a deterrent, and was not randomly applied.” However SCOTUS has ruled that certain crimes should not be crimes the death penalty can be applied such as rape. They base their views on what is known as a modern approach of “Evolving Standards of Decency”, which the court has developed based on the laws in the fifty states.
The meaning of “cruel and unusual punishment” today is far different than in Colonial times. But pinning down the modern interpretation is very difficult. The whole idea behind this was to avoid barbaric or severe punishments that were out of line with the severity of the crime committed.
“When the Declaration was issued, however, fairly gruesome punishment was meted out as a matter of course. For example, dozens of offenses, including those as minor as grand theft, were punishable by death. America's adoption of the ban on cruel and unusual punishment took place within a similar context—the men who wrote the Constitution were aware of harsh colonial practices such as repeatedly plunging low-level offenders under water.”
“While the English framers’ purpose was to outlaw savage and torturous forms of punishment, modern readers may wonder how the punishments of the day escaped censure under the lofty ban. In America, many punishments survived under the cruel and unusual punishment clause simply because they had long been permissible. Courts upheld punishments such as disenfranchisement for dueling, whipping for illegal gambling, and banishment for larceny because these were acceptable English (and hence American) practices.”
Prisoners and their supporters continue to make claims that no matter how they’re treated that treatment is “cruel and unusual”. There’s more here.