Debating the Evidence of Capital Punishment

Capital punishment terminates a human life. Is there any case at all for a doctor being in favour of it? Hippocrates; first, do no harm; do we really need to spell it out?

At a recent meeting of the Council of the World Medical Association – I represent the BMA there – there was debate over a resolution deploring capital punishment and, specifically, medical involvement. Most national medical associations were in favour of such condemnation, but not all. One appeal was to justice: he shot others, the argument runs, surely he deserves to die. Another appeal was to protecting the public: he is a terrorist, he bombed and maimed, unless we execute him, he’ll kill others.

My contribution to the discussion, fully ready to be criticised by the lawyers in the room, was that there are three possible reasons for the criminal justice system: deterrence, revenge, and protecting the public.

Taking them in reverse order: protecting the public. If a dangerous killer or rapist has been caught, the public need to be protected. Locking up the convicted criminal up is a way of doing that. It is not necessary to execute them in order to protect the public. In fact, in the USA, those handed a sentence of execution, can spend twenty years or more behind bars, as the appeals go on, so the main way the public is protected is locking up the criminal – even if the criminal has been sentenced to death. After such a time, and with the public protected, why go through with the execution?

Revenge. No doubt, advocates for capital punishment would not call it revenge, but closure, satisfaction or something of that nature for the bereaved or for society as a whole. But what else is it but revenge? Does not killing a killer mean that we have descended to his level? Eye for an eye is primitive, surely beneath a civilised society. If the organs of society do not feel moral repugnance at becoming killers, then we have a long moral argument ahead of us.

Deterrence. It could be argued that if capital punishment deterred others from committing murder, killing (executing) one person could lead to a net saving of life. It is a means and ends argument. The vile means of executing someone would be justified by the end of saving lives. The proponents of capital punishment could therefore put themselves on the side of preserving human life.

Quite apart from the question of whether doctors should be complicit in executions, what does the empirical evidence show on whether there is a deterrent effect? A friend told me that there had been several reviews of the deterrent effect of capital punishment on homicide. Some found convincing deterrent effect; others found none. My friend told me that ALL the reviews that found deterrent effect were by economists; all the reviews that found none were by criminologists.

Why?

Economists believe in incentives and rational choice. Some young man is feeling violent; he weighs up the costs and benefits of committing murder; and where the curves cross he acts. If capital punishment is in force, he thinks the costs of committing murder are too high and desists. Can you believe that?

Unlikely as it may seem that real people function this way, this view of how the world works shapes the interpretation of the evidence – i.e whether the data support a deterrent effect or not.

I had a quick look at the literature and found an interesting article (2013 Columbia Law School) from Jeffrey Fagan, Professor of Law and Public Health at Columbia. He dates a particular debate from 1975:

"...when University of Buffalo Professor Isaac Ehrlich published an influential article asserting that during the 1950s and '60s, each execution "…saved eight innocent lives" by deterring murder. Inspired by an economic model of crime developed by Professor Gary Becker of the University of Chicago, Ehrlich theorized that would-be murderers would choose between illegal and legal behavior based on the threat of execution."

Gary Becker, Nobel Prize winning economist, apparently suggests that people do make rational choices based on threat of execution. The debate now takes on a  polarised tinge: Cass Sunstein (of nudge fame) and Becker are convinced. Jeffrey Fagan, presumable closer to the “criminologist” dichotomy is most certainly not. Fagan reviews more recent studies that the economists find convincing. He rejects them on methodological grounds, among which are that the analyses did not consider other causes of fluctuations in homicide rates or the possible deterrent effects of imprisonment, as distinct from homicide. A quick look at other literature show that there are questions over the assumptions that went into the choice of instrumental variables, much beloved of econometricians. Essentially, an instrument should be correlated with execution rates but not with the “outcome”, in this case homicide rates. In that way, the independent relation between execution and homicide can be determined.

This all sounds rather familiar. I have written with passion about how economists analyse the same data we do and find the causal arrow runs from health to wealth and not, as we conclude, that features connected to socio-economic position are causal of poor health. (See: A continued Affair with Science and Judgements. International Journal of Epidemiology 2009). Same data; opposite conclusions. Here we are again.

I remain interested in why people, who purport to be empirical scientists, take such opposite views of what the evidence shows. It has to be related to starting assumptions. The interesting question then is why views on the deterrent effect of capital punishment (and the health damaging effects of social conditions) vary by academic discipline. Predictably, I side with the Professor of Law and Public Health and against the rational choice theorists, in finding the deterrent effect of capital punishment unpersuasive. But then, as a doctor, I find participation in legal execution to run counter to what we do. I am hopelessly biased by concern for human life. We all have biases that colour our view of the evidence. At least my bias does not lead to my advocacy of killing people.