Prison is the right place for Chris Huhne and Vicky Pryce While swapping penalty points for speeding to avoid a driving ban might seem low on the criminality matrix, Huhne and Pryce were convicted for perverting the course of justice, a crime that strikes at the integrity of the system itself. This is a serious common law offence that carries a maximum sentence of life imprisonment and can include intimidating witnesses, threatening judges or fabricating evidence. The Huhne case may appear victimless, but we are all its victims, because it undermines the rule of law. For this reason, the courts take an extremely dim view of those found guilty of such an offence. Prison is, therefore, a perfectly proper punishment; so why do many people feel uneasy about the incarceration of the pair? They are of previous good character, they are otherwise decent upstanding citizens. One was even in the Cabinet, for goodness" sake. Surely they were prime candidates for the non-custodial sentences ministers are always urging the courts to use to ease the prison population crisis. Moreover, it will cost thousand of pounds to keep them in jail and they are not serial criminals who might be deterred from future offending or benefit from rehabilitation. But all these considerations are, or should be, irrelevant. They reflect a popular confusion about what prison is for, largely because many people are no longer comfortable with the notion of retributive justice as a reflection of our community's moral values. It is a concept with which previous generations would have been familiar, but which we are now told to regard as antiquated. We used to call it condign punishment and it is part of the social contract that binds us together. Without it we would have vendettas and individual vengeance. It is important that penalties imposed by the courts reflect the seriousness of a crime, or victims will rightly feel aggrieved and demand an input into sentences, which is inimical to the idea of a depersonalised justice system. Although the courts dealt severely enough with Huhne and Pryce, overall the sentencing regime is more benign than it once was and far readier to accept that offenders should be given greater latitude because of their circumstances. A few years ago, I attended a talk by the American sociologist Charles Murray, who posed a number of sentencing scenarios and invited participants to select those they felt were right. The exercise was designed to distinguish between a liberal approach to punishment and a more tough-minded one. Murray's thesis was that crime had risen over the past 50 years principally because we are softer on miscreants than we used to be. One hypothesis concerned a person who had committed a serious crime, but who we knew would never commit another, even if he were not punished. Should this diminish the severity of the punishment? Murray's answer was no, a conclusion reached 250 years ago by the German philosopher Immanuel Kant, who imagined an island whose entire population was preparing to emigrate. In their midst was a sole prisoner, sentenced to death. Should the penalty be carried out even though no one would be left for the perpetrator to injure? Yes, said Kant: the punishment was deserved for the crime committed. Considerations of future harm, rehabilitation, good behaviour and the like were immaterial. The distinction is therefore drawn between a backward-looking justification for the punishment of crimes already committed and a deterministic, forward-looking rationale for going easy on offenders because they may behave better in the future. But we always have a choice to do the right thing, just as Huhne and Pryce had a choice. If they had got off lightly, how many people caught speeding would say that someone else was driving the car? Incidentally, I was exposed as a wishy-washy liberal by Murray's test, culturally overburdened with an emphasis on mitigating considerations rather than a focus on the gravity of the offence itself. It is this which should determine the magnitude of the sentence, and that is why it is right that Huhne and Pryce are now in jail.