Article by Michael Portillo on the death penalty for The Sun, 25 February 2008.

In a recent television programme I researched whether there is a painless way to execute murderers. The death penalty is widely used in United States, but now it is disputed whether the methods used are constitutional. The Eighth Amendment forbids "cruel and unusual" punishment, and the Supreme Court is to consider whether the commonly-used lethal injection fails that test.

In the death chamber at Louisiana State Penitentiary I saw that the injection is administered in three stages. The initial anaesthetic may wear off quickly. Because the second drug, pancuronium bromide, paralyses the prisoner he is unable to show any sign of pain when the third chemical, potassium chloride, gives him the fatal heart attack. In any case, patients who have been given pancuronium (which is also used in surgery) have attested that it causes excruciating pain if the anaesthetic wears off.

Apparently, a simple answer would be to kill the prisoner with a single massive overdose of anaesthetic. But that does not solve the problem because administering any injection requires medical expertise, and American doctors will not participate in killing. So prison staff insert the needles, and they can botch it. Many prisoners are drug users and finding a vein can be difficult. Sometimes the needle has been passed straight through a vein so the chemicals leak out into soft body tissue causing a prolonged death.

The older methods of killing are probably worse. The electric chair can be very messy. Even 2400 volts does not guarantee a quick end, so prison procedures specify three 15-second bursts. The executions get botched too. One electrode is attached to a cap on the prisoner's head and the current passes through sponges soaked in salty water. In one instance the prison wardens bought artificial sponges instead of natural ones, and the prisoner's head caught fire.

The gas chamber uses cyanide gas in a procedure horribly reminiscent of the holocaust. The prisoner’s pain has been compared to suffering a heart attack and brain seizure simultaneously. He may writhe for minutes. It is claimed that he could die faster by breathing calmly and deeply. I tested the theory by exposing myself to a riot control gas, which though not lethal causes intense irritation to the eyes and throat. I attempted to breathe it in but my body's reflexes took over and I resisted the gas. You cannot expect prisoners successfully to reduce how long they suffer.

Hanging can produce instant death if the length of the drop is right. But although hangmen draw up tables specifying longer drops for lighter prisoners, anatomies vary too much for this to be an exact science. Hang them too short and they suffocate slowly. Hang them too long, and the head comes off, as happened to Saddam's half brother. Decapitation is an instant death, admittedly, but it is gory. Neither the statutory witnesses nor society wants blood and guts. I therefore ruled out guillotines, firing squads and garroting too.

Almost no research has been done into how to kill humans painlessly but the humane killing of animals has been extensively investigated. One method used is hypoxia: starving the brain of oxygen.

I tested this in two experiments. First I was spun round in a human centrifuge, a sort of massive spin dryer, used to train fighter pilots. As the G-force rose my blood became heavier and drained from my head into my legs. I was on the point of blacking out, and had the spinning continued I would soon have died. The experience was weird but not painful.

Then I was placed in an altitude chamber, which simulated the effect of a plane depressurising at 27,000 feet. At that height the air contains little oxygen. Within six minutes I was hypoxic. I was unable to perform simple tasks or to put on an oxygen mask to save my life. I was close to death when the experiment supervisor had to strap it to my face. I felt no pain. In fact I was on a high as though I had been drinking.

Hypoxia can be induced more simply by making the prisoner breathe nitrogen through a mask. He would die painlessly and the procedure requires no medical expertise.

My findings did not satisfy those opposed to the death penalty. They do not want execution to be sanitised further. Some who support capital punishment were horrified to contemplate that sadistic murderers would die in a euphoric state. That might be painless, they said, but not humane to the families of the killer’s victims.

I believe my inquiry was valid. Capital punishment exists in many countries and in some, at least, the state wishes to avoid accusations of barbarism. If they seek a way to kill murderers painlessly, I recommend death by nitrogen.