You don't have to kill em to prevent em from murdering again. That's what they specialize in at prisons.
If you read the list I posted, you would not make such a ridiculous & ignorant comment.
Here's a short sample >>>
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In March 1979, a Graterford (Pa.) prison guard was
murdered brutally by an inmate. The inmate -- at the time he murdered the guard -- already was serving a life sentence for the triple murder of two infants and an elderly woman.
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In 1994, an inmate who already was serving two life sentences in the Philadelphia Industrial Correctional Center was sentenced to three more after he was
convicted of stabbing three prison guards.
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In 1995, two death-row inmates at the Florida State Prison in Starke were
killed by their fellow inmates.
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In 1999, a Beeville (Texas)
prison guard was killed by an inmate already serving a sentence for murder.
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On November 9, 1983 Associate U.S. Attorney General D. Lowell Jensen told a Senate subcommittee that it is impossible to punish or even deter such prison murders because,
without a death sentence, a violent life-termer has free rein "to continue to murder as opportunity and his perverse motives dictate."
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On October 22, 1983 at the federal penitentiary in Marion, Illinois,
two prison guards were murdered in two SEPARATE instances by SEPARATE inmates who were both serving life terms for previously murdering inmates.