Expert: John Locke - 8/24/2010

Question
Dear John, I'm currently writing a book involving lethal injections. I would like to know, what chemical would not only be the most deadly to inject in a human being but also cause instant death?

Answer
Thanks for using AllExperts. This topic gets a surprising amount of play among mystery/crime writers, who have been using poisons in their books for as long as literature has existed. First, let's define terms: instantaneous death, defined as death occurring within the shortest interval possible for us to measure, is probably not achievable with any poisons that now exist. True brain death--the irreversible loss of higher brain function--takes about 10 minutes to occur after circulation and respiration stops. There are no drugs that immediately destroy the brain in such a way as to cause instant death; there are many drugs that cause cardiac arrest and eventual death, however.

Many drugs cause immediate unconsciousness (occurring within seconds to one minute of intravenous injection) and then rapid death thereafter (occurring within minutes to one hour of injection), but neither is instantaneous. Drugs in this category would include ultra-short acting barbiturates, thiopental in particular. The anesthetic agent propofol similarly causes immediate unconsciousness and rapid death. Intravenously injected opiates like morphine and fentanyl would have a similar effect; none of these drugs, however, causes immediate death.

On the other hand, there are drugs that cause death within minutes of injection due to cardiac arrest. Potassium, given in massive overdose, is enough to trigger ventricular arrhythmias and eventual cardiac failure within minutes of IV administration. There are various neuromuscular paralytic agents--pancuronium, mivacuronium, rocuronium--that cause muscular paralysis without loss of consciousness or cardiac arrest. The person injected with these chemicals then suffocates because they are unable to move their diaphragm to breathe. Respiratory arrest leads inevitably to cardiac arrest with brain death following thereafter.

Potassium ion and/or the anesthetic agents listed above would strike me as some of the most dangerous to inject into a person with the intent of killing them.