Perhaps the most vigorous one revolves around the possibility (or inevitability) of wrongful convictions causing the execution of innocent people. High-profile campaigns by organizations like the Innocence Project ensures that this line of argument will remain active; the Project uses DNA testing to exonerate convicted criminals. To date, 266 convicts have been exonerated, including 17 on death row.

Within libertarianism, capital punishment remains a point of unsettled theory. Libertarians generally agree on the imprudence of granting government the power of life and death but this important concern is not a fundamental one. The question of capital punishment would also confront a private justice system.

Could a private court properly deliver a death sentence?

To rephrase the question: can you justly kill a stranger who has done you no personal harm and who poses no immediate threat to others? This is what a courtroom does when it sentences an already imprisoned man to die.

If capital punishment is proper, then it is based on the right of self-defense, the right to kill another person who uses deadly force against you. Once the threat of deadly force has gone, however, courts – or, more broadly, a legal system – take over. If people were permitted to personally execute yesterday's aggressor in his sleep, it would become impossible for third parties to tell victims from perps. A third party might well come to the defense of the aggressor, killing the victim-vigilante in the process. Thus, one role of a proper court system is to provide the public objectivity that prevents society from resembling a Hobbesian war of all against all.

In short, if an individual has the right to personally kill another during deadly aggression, then he can properly delegate that right to a private court.

But what of the aggressor and his rights? The 19th century classical liberal Herbert Spencer believed rights could be alienated through acts of aggression. For example, by murdering, a man stripped himself of the humanity required to claim a reciprocal right to life and, so, he reduced himself to the level of a base animal. The 20th century Austrian economist Murray Rothbard argued that an aggressor forfeited rights to the extent that he had violated them himself.

The foregoing case for free market capital punishment is counties away from conclusive. The imposed brevity of discussion means that far more is unexplored than touched upon. Moreover, capital punishment raises many troubling and unresolved questions. For example, if it is proper to kill an aggressor, why not just hideously torture him for months instead? After all, the imposition of pain is a lesser punishment than death.

Conclusion

For libertarians, however, capital punishment may remain a theoretical football.

The government is in charge of all aspects of the death penalty and this one fact presents an insuperable barrier to advocacy. It is not merely that the encroaching state cannot be trusted with power; it is, as the Innocence Project spotlights, that the system is rampantly bureaucratic and inefficient.

In an increasingly militarized and militant society, capital punishment is likely to expand both in definition and application. In Louisiana and Florida, the death penalty covers aggravated rape. Connecticut includes drug trafficking that results in a death. Alabama will execute you for airplane hijacking.

As definition and application expand, it becomes increasingly dangerous for the government to have the institutionalized 'right' to execute.

In short, whether libertarian theory can embrace capital punishment is a fascinating debate but, in the current reality, there is only one practical answer: ban the procedure.

For more commentary, please visit WendyMcElroy.com.