A botched execution in Oklahoma has renewed debate about the practice of government-sanctioned killings as states ponder an effective way to carry out a death sentence.
On Tuesday, 38-year-old convicted killer Clayton Lockett struggled in agony for 40 minutes, "writhing, clenching his teeth and straining to lift his head off the pillow " before the execution was called off, according to the Associated Press.
Lockett later died of a massive heart attack that night.
The ugly results of Locket's execution -- and a shortage of proven lethal injection drugs -- have left states in a scramble. Some have even suggested bringing back more archaic forms of killing people.
But according to the Death Penalty Information Center, a national nonprofit that offers analysis and information on capital punishment, all methods of execution are problematic. And a recent op-ed in the Boston Globe points to research that found that between 1890 and 2010, about 3 percent of executions were botched and 7 percent of lethal injections didn't go as planned.
Infographic by Jan Diehm for The Huffington Post.
Read on to learn more about each of these methods:
There have been three convicts killed via hanging since the death penalty was reinstated in 1976. The AP notes, "If done correctly, an inmate's neck breaks instantly upon the body's drop, but it can also lead to prolonged strangulation." The Death Penalty Information Center says that in a hanging that goes awry, "the [prisoner's] face becomes engorged, the tongue protrudes, the eyes pop, the body defecates, and violent movements of the limbs occur."
Hanging was the primary method of execution in the U.S. before 1890.
This method was most often used in the 19th and 20th centuries, according to the AP. When an inmate dies by firing squad, five executioners stand 20 feet away from the prisoner and fire at his or her heart. Ideally, the inmate dies from blood loss after their heart ruptures. But, as the Death Penalty Information Center notes, "If the shooters miss the heart, by accident or intention, the prisoner bleeds to death slowly."
The AP reports that many experts believe death by firing squad is the most humane form of execution available.
Introduced in 1924, 11 inmates have been executed via gas chamber since 1976, according to the AP. It's still an option in three states.
For execution by this method, the condemned person is strapped to a chair in an airtight chamber. Below the chair rests a pail of sulfuric acid. A long stethoscope is typically affixed to the inmate so that a doctor outside the chamber can pronounce death. Once everyone has left the chamber, the room is sealed. The warden then gives a signal to the executioner who flicks a lever that releases crystals of sodium cyanide into the pail. This causes a chemical reaction that releases hydrogen cyanide gas.
According to the Death Penalty Information Center, former California penitentiary warden Clifton Duffy described what happens to inmates like this: "At first there is evidence of extreme horror, pain, and strangling. The eyes pop. The skin turns purple and the victim begins to drool."
The site also says Dr. Richard Traystman of John Hopkins University School of Medicine told the New Republic in 1991, "The person is unquestionably experiencing pain and extreme anxiety ... The sensation is similar to the pain felt by a person during a heart attack, where essentially the heart is being deprived of oxygen."
The history of the electric chair actually has ties to Thomas Edison, who, as TIME reported, secretly funded research into the electric chair being made by one of his competitors so that consumers wouldn't buy electricity from the rival business.
The first electrocution took place in 1890 in New York.
A 1994 piece in the Philadelphia Inquirer featured this quote from former U.S. Supreme Court Justice William Brennan, according to the Death Penalty Information Center:
The prisoner's eyeballs sometimes pop out and rest on [his] cheeks. The prisoner often defecates, urinates, and vomits blood and drool. The body turns bright red as its temperature rises, and the prisoner's flesh swells and his skin stretches to the point of breaking. Sometimes the prisoner catches fire. ... Witnesses hear a loud and sustained sound like bacon frying, and the sickly sweet smell of burning flesh permeates the chamber.
By far the most common method of state-sanctioned killing today, the first lethal injection took place in 1977 in Oklahoma, the same state that botched Lockett's execution.
The New York Times sums up some of the recent problems with this method:
A number of factors have conspired to produce painful scenes in the death chamber, experts say: an ill-conceived drug formulation clung to by many states; the lack of medical expertise among people planning and carrying out executions; and, more recently, drug shortages that have pushed prison officials to improvise lethal cocktails and buy drugs from loosely regulated compounding pharmacies.
The Death Penalty Information Center also notes that, because doctors are ethically prohibited from administering execution drugs, inexperienced medical workers can sometimes make mistakes like injecting the drugs into a muscle, causing "extreme pain."
Correction: The original map left out lethal injection icons on Nebraska and South Dakota. The map has been updated to reflect that both states authorize lethal injection.