A lethal injection execution room.Corbis Images

On Tuesday, Oklahoma prison officials carried out the execution of inmate Clayton Lockett using a secret drug combination to perform the lethal injection. Lockett and another inmate due to be put to death had attempted to secure a stay of execution until the source of the drug could be made public, but Oklahoma Gov. Mary Fallin ordered the punishments to be carried out, overruling the State Supreme Court, which had granted a temporary halt.

As would be expected with an untested drug cocktail, the execution did not go as planned. After falling unconscious, Lockett then convulsed violently and began muttering incoherently. Sixteen minutes into the execution, authorities surrounded Lockett with a curtain to keep him out of view of witnesses. It took 43 minutes for him to die. The cause of death was ruled a heart attack.

Lethal injection was introduced as a means of sanitizing the death penalty, avoiding the drama and gore of execution methods of the past. But just because the methods have changed over the course of the history of the capital punishment doesn't make the outcome any different.

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Although ancient tribal societies and civilizations no doubt had some form or another of the death penalty, Hammurabi's code, dating back to the 18th century B.C., is the oldest written set of laws ever discovered. As such, it also presents the earliest historical record of capital punishment.

The death penalty applied to some 30 crimes. For some, such as theft of a palace treasury, kidnapping, selling stolen goods or even disorderly conduct in a tavern, the method of execution goes unspecified. In other cases, however, the application of capital punishment is more precise. For example, in cases of burglary, the code calls for a hanging on the spot. Theft during a fire would result in a burning, again on the spot. Crimes such as adultery or rape would call for the criminal(s) to be drowned.

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Ancient Greek laws are inscribed on a stone plinth near Delphi.Corbis Images

Like Hammurabi, other ancient societies eventually developed their own set of written laws that included the death penalty, such as the Hittite Code in the 14th century B.C. or the Roman Law of the Twelve Tablets in the fifth century B.C.

One set of ancient laws notoriously went further than any other before or since in its administration of capital punishment. Dating to the seventh century B.C., the Draconian Code of Laws called for anyone convicted of any crime to receive the death penalty.

As Plutarch recounts in the Life of Solon, Draco, the ancient Greek legislator behind the laws, reportedly stated that he believed those who committed lesser crimes were deserving of death, and those who were responsible for more serious crimes couldn't receive a punishment worse than death, though Draco would prescribe it if one existed.

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Jesus Christ is crucified by the Romans in this painting.Corbis Images

The earliest methods of execution were intended to cause suffering or even torture the criminal. The Romans, for example, seemed to have a talent for diversity among their means of carrying out a death sentence, including impalement, death by crushing, feeding a criminal to animals and crucifixion.

Given that Christians eventually became a favorite target of Roman authorities for execution, it should come as no surprise that some of the earliest opponents of the death penalty -- in the Western World at least -- were Christians, viewing capital punishment as contrary to Christian ethic. As Pope Gregory I (590-604) said, as told in the book "Cruel & Unusual: The American Death Penalty and the Founders' Eighth Amendment": "Since I fear God, I shrink from having anything whatsoever to do with the death of anyone."

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In 1066, William the Conqueror abolished the death penalty, one of the earliest rulers to do so, except in times of war. The change in the law certainly couldn't be considered much of an act of mercy, however. William instead preferred that criminals be subjected to excruciating punishments such as blinding, torture or castration.

The prohibition on the death penalty was eventually withdrawn by William's son, Henry I, in 1108. In fact, the death penalty was expanded, with more crimes being judged capital offenses and more methods of capital punishment introduced. Starting in the 10th century, hanging was the most common form of execution in the United Kingdom. Other methods, including boiling a convict alive or drawing and quartering a prisoner, were eventually introduced in the later Middle Ages.

England would retain the death penalty as a punishment for crimes up until 1965. The British even brought it with them to their colonies in the New World.

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An illustration of an execution taking place in colonial America.Getty Images

Captain George Kendall has the distinction of being the first recorded execution in the U.S. colonies, accused in the Jamestown colony in 1608 of being a spy for Spain.

Each of the early colonies had their own set of laws that judged which crimes would be capital offenses. In 1612, for example, Virginia governor Sir Thomas Dale instituted the Divine, Moral and Martial Laws, which made actions such as trading with Indians or blasphemy punishable by death. In 1665, New York implemented the Duke's Laws (PDF), which calls for the death penalty for anyone who "den the true God and his Attributes," among other capital offenses.

Some colonies were more lenient. Pennsylvania only allowed for capital punishment for the crimes of murder or treason, for example.

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Cesare Beccaria could be considered the father of the death penalty abolition movement. In 1764, Beccarria published a series of essays titled, "On Crimes and Punishments," which was translated into English three years later.

Invoking the ideals of the Enlightenment and echoing past abolitionist philosophers, Beccaria, citing Montesquieu, asserts at the opening that "Every punishment, which does not arise from absolute necessity... is tyrannical." If a punishment for a crime proves to be useless, in that it is not of public benefit or that it doesn't prevent future crimes, then that sentence is contrary to justice and the social compact that "equally binds the highest and lowest of mankind," according to Beccaria. This violation of the social compact is "an introduction to anarchy."

Beccaria's ideas spread throughout Europe, leading to some reforms. In the United States, Thomas Jefferson, influenced by Beccaria's writings, made an attempt to revise Virginia's laws to only call for the death penalty only in cases of murder or treason, but his efforts failed. Other founding fathers, such as Benjamin Franklin, General William Bradford and Benjamin Rush, also were influenced by Beccaria.

By the time the United States won its independence from the British, the former colonies all had laws on the books calling for the death penalty for certain crimes. In fact, by then, Rhode Island was the only colony that had less than 10 crimes on its books that were considered capital offenses.

A view of the Preamble of the U.S. Constitution.Corbis

Ratified in 1791, the Eighth Amendment of the U.S. Constitution, part of the Bill of Rights, prohibits the government from imposing "cruel and unusual punishments" for crimes. Some punishments, such as torture, are explicitly forbidden. The amendment also prohibits sentences that aren't proportional to the crime committed.

Since the 19th century and even up to today, various cases have challenged the meaning of the term "cruel and unusual." While it has been applied to forbid certain means of execution, it doesn't in any way prohibit the use of capital punishment as a response to crimes. Controversy over public hangings, for example, first arose in the 1830s under the argument that they were "cruel," so states resorted to private hangings instead closed from public view. (The last public execution, however, took place 100 years later.)

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An illustration of the public execution by hanging of convicted murderers Joseph Hetherington and Philander Brace in San Francisco in 1856.Corbis Images

Beginning in the 19th century, several states began rolling back their use of the death penalty by limiting the crimes to which it applied. In 1846, Michigan was the first state to abolish the death penalty for all crimes except treason, and was later followed by Rhode Island six years later that abolished capital punishment entirely. Some states, like Maine, went back and forth, abolishing the death penalty, then reenacting it, only to abolish it again.

States also increasingly began to allow for judicial discretion in sentencing, no longer requiring capital punishment for certain crimes. Death penalty opposition slowed down with the Civil War in the middle of the century. And by the end of the century, while abolitionists were once again making inroads in rolling back capital punishment, new means of executing prisoners were being devised and implemented.

A prisoner is executed by electric chair in this photo taken in 1908.Corbis Images

Thomas Edison attempted to demonstrate the dangers of alternating current electrical systems by publicly electrocuting animals to death. These demonstrations spawned the electric chair, a thoroughly modern means of carrying out a death sentence. The first person to be executed with this method was William Kemmler in 1890. Three and a half decades later, cyanide gas was introduced as a means of execution, as it was thought to be a more humane way of putting prisoners to death.

These execution methods were arriving at a time when the use of the death penalty in the United States was once again on the rise. The violence of the Prohibition era, the desperation of the Great Depression, the fears of the World War II years and the paranoia of a Communist insurrection lead to a revival of capital punishment. Several states that had once renounced the death penalty even began implementing it again.

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The mid-20th century saw a revival in the anti-capital punishment movement, owing to widely published research showing the inefficacy of the death penalty, as well as publicized first-hand accounts of prisoners on death row. In fact, in 1966, support for the death penalty reached an all-time low, with only 42 percent of American in favor of its use, according to Gallup Poll.

Cases were brought before the courts that challenged the legality of capital punishment. In 1972, in the case of Furman v. Georgia, the U.S. Supreme Court ruled the capital punishment laws as they were written were in violation of the Eighth and Fourteenth Amendments to the Constitution. After states rewrote and passed new death penalty laws in the wake of Furman, the Supreme Court in 1976 upheld the constitutionality of capital punishment.

A view of a lethal injection execution room.Corbis Images

With states now permitted to once again employ the death penalty, they began to look for new, more humane and cheaper ways of carrying out a sentence. Lethal injection seemed to fit the bill as it appeared to be a cruelty-free means of putting someone to death, while costing less than $20.

Oklahoma, the same state in which Lockett was executed, was the first to pass a lethal injection law. In 1982, Texas became the first state to execute a prisoner using this method, and other states soon followed suit, as other means of execution were gradually phased out. The last execution by hanging took place in 1996; the gas chamber was last used in 1999; and a firing squad was employed to carry out a sentence for the last time in 2013.

Even as the courts limited who was eligible for capital punishment in the 1980s and 1990s, deeming minors and the insane to be ineligible for the death penalty, Americans' support of the punishment in fact grew over those years to an all-time high of 80 percent in 1994. That same year, then-President Bill Clinton significantly expanded the definition of criminal offenses potentially meriting capital sentences to include terrorism, large-scale drug trafficking and carjackings resulting in a homicide.

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A guard inspects cells on death row in San Quentin penitentiary in California.Corbis Images

Currently, 18 states and the District of Columbia do not have laws on the books that allow for capital punishment. Support for the death penalty is once again on the decline, with 60 percent of American supporting it. Thanks to DNA evidence and advocacy groups like the Innocence Project, more and more inmates wrongfully on death row have been exonerated. A recent study also found that some 4 percent of prisoners on death row were wrongfully convicted.

Internationally, the United States is one of 22 countries that carried out executions in 2013. The United States carried out 39 executions in 2013, down from 43 in 2012 and following a pattern of decline since 1999. More than 3,000 inmates are currently waiting on death row for their day to arrive.