An appropriate punishment for Christian Nielsen simply doesn’t exist.

On Thursday, an Oxford County Superior Court justice gave the quadruple-murderer four concurrent life sentences for the killings that shocked Maine over Labor Day 2006. Nielsen, a boarder at the Black Bear Inn B&B in Newry, took the lives of four innocents over three days for his own, unexplainable reasons.

His attorneys, who barely spoke to their client, sought 45 years in prison for him. With good behavior, this could have meant Nielsen’s release from prison around age 70, which would have been a severe miscarriage of justice.

Nobody who kills in cold blood like Nielsen should be privileged to taste the sweet air of freedom again.

Yet the alternative proposed by the prosecution – four consecutive life sentences – was technically warranted, but practically meaningless. There was only one life to take away from Nielsen, his own, despite the heartbreak and horrors he wrought upon his four victims’ families.

From the beginning, Nielsen was an enigma. A loner, who we learned later dreamed for years of being a serial killer. A murderer without real motive, only the terrible means and easy opportunity. An aggressive jail inmate who attacked others with crude weapons, but then subjected himself to starvation and self-inflicted wounds.

Most of all, with Nielsen we were confronted with the rarest of killers: the remorseless, cold, calculating sort, who knew the exact gravity of what he was doing, and did it anyway. He could offer neither rationale, excuse nor, surprisingly, even a creative something to blame for the murders.

Nielsen would neither work with his attorneys, contest his guilt, nor profess some mental illness that triggered his spree. He appeared content to be judged as someone who killed four people, the first for no reason at all, and the others for the oldest of reasons – to cover his tracks.

Punishments didn’t seem to make a difference to him. Nothing did. Nielsen’s icy detachment made him an unconventional criminal; in an era where perpetrators of heinous acts have ready-made maladies and outrageous explanations, Nielsen was unique in proclaiming himself nothing but a grotesque killer.

Sentencing this kind of monster appropriately was impossible. Justice requires penitence, and Nielsen has none. There’s nothing more Justice Robert Crowley could have done except imprison him for good.

But Crowley didn’t lock Nielsen away. This killer won’t be rehabilitated, but rather warehoused. Instead, the justice has done something far more important.

He’s keeping Nielsen away from us.