Accused Satanic Murderer Miranda Barbour -- Spare Me From the Death Penalty!

Miranda Barbour -- who claims to have committed between 22 and 100 murders -- claims she should not be subject to the death penalty because it's "cruel and inhuman punishment."

In legal docs filed by her lawyer, Miranda argues it would be unfair to put her to death -- even if convicted -- because "the criminal justice system is fallible, thereby subjecting inappropriate persons to the death penalty."

As for whether Barbour is an "inappropriate person" ... hard to make the argument since she confessed to cops. But her lawyer has an answer for that ... asking the court to throw out her confession on grounds cops violated her constitutional rights.

Barbour's lawyer says she repeatedly asked for an attorney, only to be denied.

But there's a big snag ... Barbour then confessed to knifing a man she met on Craigslist and a lot more last Thursday to a local reporter. That confession is fair game.