There is no technology so beneficial that someone somewhere isn't thinking about how to use it to hurt people. That even holds true for means of rejuvenation, ways to eliminate the vast and terrible cost of degenerative aging, all of the suffering, the tens of millions of deaths each and every year. Some people look at the possibilities for near future human rejuvenation and think "I've figured out a way to use this to more effectively hurt the groups of people that we don't like."
Some argue that retributive punishment (reactionary punishment, such as imprisonment) should be replaced where possible with a forward-looking approach such as restorative justice. I imagine, however, that even opponents of retributive justice would shrink from suggesting that [the worst of offenders] should escape unpunished. I assume - in line with the mainstream view of punishment in the UK legal system and in every other culture I can think of - that retributive punishment is appropriate in [some cases].
Within the transhumanist movement, the belief that science will soon be able to halt the ageing process and enable humans to remain healthy indefinitely is widespread. Dr Aubrey de Grey, co-founder of the anti-ageing SENS Research Foundation, believes that the first person to live to 1,000 years has already been born. The benefits of such radical lifespan enhancement are obvious - but it could also be harnessed to increase the severity of punishments. In cases where a thirty-year life sentence is judged too lenient, convicted criminals could be sentenced to receive a life sentence in conjunction with lifespan enhancement. As a result, life imprisonment could mean several hundred years rather than a few decades. It would, of course, be more expensive for society to support such sentences. However, if lifespan enhancement were widely available, this cost could be offset by the increased contributions of a longer-lived workforce.
When the state enforces a monopoly on criminal dispute resolution, as is the case in most regions of the world these days, the only interests served are those of the state employees and appointees involved. Even in legitimate cases you end up with the worst of all worlds: the system remains based upon serving a desire for vengeance and appeasing the mob, imprisonment (as opposed to banishment or outlawing) removes the ability for an offender to work towards restitution, and those with the greatest interest in obtaining justice and resolution are cut out of the decision-making process. There is worse, however. The methods and traditions created for the worst offenders are soon enough applied to everyone without sufficient power and influence to buy their way clear. Modern systems of state justice are terrible impersonal engines, set upon expansion, and all too quickly used for self-empowerment and suppression of dissent by politicians and bureaucrats.