Like any other execution method, the people most qualified to give you an answer can no longer do so. But we can make some conclusions from what we know about human physiology and the mechanics of death by electrocution.
The process of electrocution is pretty straight forward. You will be strapped to a hard backed wooden chair by leather belts at your wrists, ankles, forearms, chest and waist. Electrodes will be attached to the crown of your head and one or both of your calves. The electrodes will be faced with sponges soaked in a saturated brine to conduct the electricity into your body and reduce burning. On command from the warden, the power supply will be activated, delivering a fatal electric shock through your body at the electrodes. Most electric chairs deliver somewhere in the area of 5–13 amps of alternating current at between 1,700–2,500 volts. Multiple shocks are applied prior to checking for signs of life. The process is often more of an art than a science; executioners developed their own particular techniques through a process of trial and error.
If done properly the sheer force of the electricity should depolarize and destroy your brain and central nervous system followed by disrupting the pacemaker in your heart causing cardiac arrest. As has been attested to by lineman who have suffered accidental electrocutions but survived, loss of consciousness was instantaneous upon contact with a high voltage source. So, if you’re going to die in a well designed and properly maintained electric chair and executed by a competent executioner, it must be something like a cessation of feeling. In one instant you’re sitting blindfolded in darkness in a hard wooden chair, the sensation of the leather straps pinioning you into the chair, the cold wetness of the electrodes on your head and legs then BANG!!! – the next instant unconsciousness and……whatever lies beyond death (if anything).
What happens to your body is not a pretty sight.
Your skeletal muscles will tense and contract maximally under the force of the current. You will probably defecate and urinate uncontrollably, your skin will turn bright red, then white. There are almost always first and second degree burns around and under the sponges from electrothermal heating of the nearby tissue due to the extreme current flux at the electrodes. When the power is shut off you will slump down in the chair against the restraints. There will be an odious smell of a mixture of burnt flesh, singed hair, urine and feces in the death chamber.
If the execution is not properly done and with defective equipment, the nightmare only intensifies. The electric chair would probably be a horrible way to die if unconsciousness is not instantaneous. The sensation of a botched judicial electrocution, I’d guess, must be like a massive, jagged splinter being driven through your entire body followed by the sensation of being on fire after a few seconds. If the sponges are absent or improperly moistened with brine, both they and the skin under them can catch fire. A nightmarish spectacle of electrical arcing between the electrodes and the convicts body can occur as did in the executions of John L Evans and Joseph Tafero in Alabama and Floride, respectively. Oftentimes the electric shocks can leave the body mangled and in a vegetative state with the heart still beating and the convict breathing, leaving the prison staff with no other choice but to continue applying jolts of electricity until death occurs. Use of excessive amounts of electric current can cook the flesh on your bones, similar to that of a cooked chicken. The skin can slough off and fall off the meat, as is particulary revolting for the prison staff to deal post execution, as they unstrap and remove the dead convict from the chair. Additionally, some doctors have claimed that electrocution may actually stimulate parts of the brain associated with fear and nightmarish imagery. Quite an ominous prospect, especially if the state has to give you 5 or 6 jolts of electricity before you finally die.
There was only one person to have survived an electrocution and been interviewed afterward about the ordeal. Willie Francis, a 17 year old youth was supposed to be electrocuted for a murder at St Martin’s Parish Jail in Louisiana on May 3, 1946. But a poorly wired portable electric chair and a drunk executioner failed to deliver a shock strong enough to kill him before the generator was damaged. Francis claimed later that the experience was “plum miserable” and that it had made his mouth taste like cold peanut butter and made him hallucinate little pink and blue speckles. He screamed during the ordeal and told his keepers to “TAKE IT OFF!!!!!” as the shock was applied. Francis remained on death row for another year after the botched execution while his lawyers argued that a second attempt to kill their client would violate his Fifth Amendment protection against double jeopardy. Louisiana ex rel Francis v Resweber, 329 U.S. 459 (1947) ultimately went before the United States Supreme Court, but in a 5–4 decision, the Court turned down this argument, stating that Francis right to protection from double jeopardy had not been violated as his sentence had not yet been carried out. On May 9, 1947, Francis was successfully electrocuted a second time.