Lethal Injection(01 of17)
Open Image ModalUntil 2010, most states used a three-drug combination: an anesthetic (pentobarbital or sodium thiopental), a paralytic agent (pancuronium bromide) to paralyze the muscle system, and a drug to stop the heart (potassium chloride). Recently, European pharmaceutical companies have refused to sell drugs to the U.S. for use in lethal injections, requiring states to find new, untested alternatives. (credit:AP)
Gas Chamber(02 of17)
Open Image ModalGas chambers, like this one pictured at the former Missouri State Penitentiary in Jefferson City, Mo., were first used in the U.S. in 1924. In the procedure, an inmate is sealed inside an airtight chamber which is then filled with toxic hydrogen cyanide gas. Oxygen starvation ultimately leads to death, but the inmate does not immediately lose consciousness. (credit:AP)
Electric Chair(03 of17)
Open Image ModalThe first electric chair was used in 1890. Electrodes attached to an inmate\'s body deliver a current of electricity. Sometimes more than one jolt is required. (credit:AP)
Hanging(04 of17)
Open Image ModalHanging was used as the primary method of execution in the U.S. until the electric chair\'s invention in 1890. Death is typically caused by dislocation of the vertebrae or asphyxiation, but in cases when the rope is too long, the inmate can sometimes be decapitated. If too short, the inmate can take up to 45 minutes to die. (credit:AP)
Firing Squad(05 of17)
Open Image ModalThis Old West-style execution method dates back to the invention of firearms. In a typical scenario in the U.S., the inmate is strapped to a chair. Five anonymous marksmen stand 20 feet away, aim rifles at the convict\'s heart, and shoot. One rifle is loaded with blanks. (credit:AP)
Beheading(06 of17)
Open Image ModalDecapitation has been used in capital punishment for thousands of years. Above is the chopping block used for beheadings at the Tower of London. (credit:Wikimedia Commons)
Guillotine(07 of17)
Open Image ModalInvented in France in the late 18th century during the French Revolution, the guillotine was designed to be an egalitarian means of execution. It severed the head more quickly and efficiently than beheading by sword. (credit:Kauko via Wikimedia Commons)
Hanging, Drawing and Quartering(08 of17)
Open Image ModalA punishment for men convicted of high treason, \"hanging, drawing and quartering\" was used in England between the 13th and 19th centuries. Men were dragged behind a horse, then hanged, disemboweled, beheaded, and chopped or torn into four pieces. (credit:Wikimedia Commons)
Slow Slicing(09 of17)
Open Image ModalAlso called \"death by a thousand cuts,\" this execution method was used in China from roughly A.D. 900 until it was banned in 1905. The slicing took place for up to three days. It was used as punishment for treason and killing one\'s parents. (credit:Carter Cutlery/Wikimedia Commons)
Boiling Alive(10 of17)
Open Image ModalDeath by boiling goes back to the first century A.D., and was legal in the 16th century in England as punishment for treason. This method of execution involved placing the person into a large cauldron containing a boiling liquid such as oil or water. (credit:Wikimedia Commons)
Crucifixion(11 of17)
Open Image ModalCrucifixion goes back to around the 6th century B.C.used today in Sudan. For this method of execution, a person is tied or nailed to a cross and left to hang. Death is slow and painful, ranging from hours to days. (credit:Wikimedia Commons)
Burning Alive(12 of17)
Open Image ModalRecords show societies burning criminals alive as far back as the 18 century B.C. under Hammurabi\'s Code of Laws in Babylonia. It has been used as punishment for sexual deviancy, witchcraft, treason and heresy. (credit:Pat Canova via Getty Images)
Live Burial(13 of17)
Open Image ModalExecution by burial goes back to 260 B.C. in ancient China, when 400,000 were reportedly buried alive by the Qin dynasty. Depending on the size of the coffin (assuming there is one), it can take anywhere from 10 minutes to several hours for a person to run out of oxygen. (credit:Antoine Wiertz/Wikimedia Commons)
Stoning(14 of17)
Open Image ModalThis ancient method of execution continues to be used as punishment for adultery today. (credit:Wikimedia Commons)
Crushing By Elephant(15 of17)
Open Image ModalThis method was commonly used for many centuries in South and Southeast Asia, in which an elephant would crush and dismember convicts as a punishment for treason. (credit:Wikimedia Commons)
Flaying(16 of17)
Open Image ModalRecords show flaying, the removal of skin from the body, was used as far back as the 9th century B.C.\n (credit:Michelangelo/Wikimedia Commons)
Impalement(17 of17)
Open Image ModalRecords show this execution practice used as far back as the 18th century B.C., where a person is penetrated through the center of their body with a stake or pole. (credit:Wikimedia Commons)