Offering the choice between a life without freedom and death is the humane thing to do
Some crimes deserve a strong penalty, and life imprisonment is that strong that we should consider giving those sentenced for life another option. Parole for those imprisoned for decades has risks, and defies the point of a life sentence. When, on the other hand, freedom is inseparable from life, some might find a life sentence unbearable. In that case, giving the option to choose for a death sentence instead is the humane thing to do.
Life imprisonment is often exactly what it says: the rest of your life in prison. Normally, only the worst offenders are faced with this penalty. They probably deservedly got sentenced for life. And, although a prisoner may feel some penalty is justified, after more than a decade of prison, he will start to despise society. From there on, re-socializing and bringing someone back to society seems a mission destined to fail more often than not. And granting a pardon to someone that did not expect to be set free, might be riskier than desired. Life imprisonment hence should be what it says: the rest of your life in prison.
Is a life sentence then really more humane?
Most people value their freedom and see it as an inseparable part of their life. Life imprisonment, intentionally, severs this link between life and freedom. Consequently those in prison for life, that attach a high value to freedom, might feel painfully hopeless. To some, it might be unbearable. Should they have the option to choose death over a life without freedom? Freedom is so ingrained in life, in constitutions for example, that it is arguably inhumane to take it for life without any alternative, like death.
In practice, we would choose life over death?
What would prisoners choose, when they could choose between life imprisonment, and a death sentence? End of 2007, New Jersey abolished the death penalty, and gave those on death row the option of changing their death sentence to life imprisonment without the possibility of parole. Although, in practice there would be no difference as New Jersey would not execute death sentences, all prisoners chose to change to life imprisonment. Possibly, people prefer life (without freedom) over death, but we cannot be sure.
In Belgium on the other hand, a rapist and murderer was eventually denied the right to die, despite his request. His reasoning basically follows the reasoning here: a life imprisoned (with psychological pain) is not worth living. In his particular situation, suffering from his sick sexual urges, being in prison for life is especially hard to bear. On the other hand, he was denied treatment too. Rationally, it must be discomforting to society to treat incarcerated that bad, that they prefer to die. So this case only hints at what some might choose, given the option.
What is humane, is personal
In conclusion, when a life without freedom is a hopeless life, offering the choice to die is the humane thing to do. As long as we resist the urge to drive imprisoned to death. Only an individual can ultimately decide what is more humane to him or her. That is the whole point of abolishing death sentences: we as a society want to be (one step) more humane than murderers. To some, life without freedom might be more inhumane than death, and death as an alternative should therefore be on the table.