Generally, there are about two botched executions each year in the United States. This fact alone is enough to make one hate the death penalty. Reading about them is the best way to understand:
Even when the death penalty goes well, the physical pain caused by electrocution, the electric chair, hanging, or lethal injection is utterly unquantifiable. And the psychological pain - including that of waiting for the execution - is so great that many death row inmates lose all individual personality traits. Robert Johnson, a criminologist, calls it "death of the personality".
But botched executions are even worse. Amnesty has these snippets:
"At a 1990 Florida execution, a malfunction of the electric chair equipment caused flames to leap six inches above the prisoner's head each time the current was turned on. In 1992, a prisoner in Oklahoma had a violent reaction to the drugs used in the lethal injection. While he gasped and gagged violently, the muscles in his jaw, neck and abdomen reacted spasmodically. Eleven minutes elapsed before the man died. In 1994 it took five minutes for David Lawson to die in North Carolina's gas chamber. During that time he screamed, 'I'm human! I'm human!'."
The Death Penalty Information Center has examples of two botched executions in 1990, one in 1991, four in 1992, one in 1994, one in 1995, one in 1996, three in 1997, and one so far in 1998.
October 1990 saw blood spew all over a convict's face as he was executed. August 1991 saw an electric chair fail to kill Derick Peterson first time; he had to be electrocuted twice. In January 1992, Arkansas officials took 50 minutes to find a suitable vein in Rickey Rector's arm in order to lethally inject him. Five people worked simultaneously to try to find one. Witnesses to the execution were not allowed to watch. In March 1992, Robyn Parks had a violent reaction to the drugs he was administered through lethal injection; his jaw, neck and abdomen reacted violently for 45 seconds. He did not die until 11 minutes later.
In April 1992, it took Texan authorities 45 minutes to find a suitable vein in Billy White's body; eventually White had to help them. The following month, in the same state, Justin May had a violent reaction to lethal injection, going into long spasms of coughing and gasping. When he died, his eyes and mouth were still open.
In May 1994, Illinois found that one of the lethal drugs had blocked up the tube through which they were injecting the drugs into John Gacy's arm. The witnesses to the execution were not allowed to watch as the tube was replaced. In May of the following year, Missouri took 30 minutes to kill Emmitt Foster. Seven minutes after the chemicals had begun flowing into his arm, the blinds were drawn so that witnesses could not watch. They were reopened three minutes after Foster's death, after he had been injected with chemicals constantly for half an hour.
In July 1996, it took an hour and a half for Indiana to murder Tommie Smith. 35 minutes were spent on trying to find a way to lethally inject him; a vein could not be found, so they inserted an angio-catheter into his heart. He remained conscious throughout the operation. In March of the following year, Florida killed Pedro Medina; foot-high flames sprung up from the right side of his head and burned for six to ten minutes; the smell of burning human flesh filled the witness room. Two months later, Oklahoma took more than 10 minutes to kill Scott Carpenter; the procedure caused him to have 18 violent convulsions, and 8 milder ones; his face turned yellow; two minutes before he died, it turned deep purple and grey. In June of 1997, it took South Carolina 40 minutes to find a suitable vein on Michael Elkins. And in April 1998, it took two attempts (separated by 15 minutes) to kill Joseph Cannon. Officials preventing witnesses from watching after the first attempt failed.