"Abolishing capital punishment in a kind of despair over its fallibility would... would tell the public that our laws and courts and juries are fundamentally incapable of delivering what most Americans consider genuine justice.."

Ross Douthat write:

It could encourage a more cynical and utilitarian view of why police forces and prisons exist, and what moral standards we should hold them to. And while it would put an end to wrongful executions, it might well lead to more overall injustice.

I've never understood why people who don't trust convictions agonize over the death penalty but blandly accept life imprisonment.