This week, Virginia executed Paul Powell for murdering a 16-year-old girl and raping and attempting to murder her 14-year-old sister. Reading the details of the crime, your instinctive response is utter revulsion and a cry for justice to be done. But state-sanctioned killing -- unless it is for reasons of national security -- is not something we as a society should be doing. In America, 139 people on death row have been exonerated. And a study on death penalty appeals found two-thirds of all death sentences were overturned due to serious errors, including prosecutorial misconduct. Then there is the cost: it is much more expensive to execute a prisoner than to send him to prison for life. For example, California could save $125 million a year if it eliminated the death penalty. That's a lot of money for a state cutting social services to the bone. It's time for the death penalty to be put to death.