I think it would be better to amend the constitution to deny the states the right to allow Capital Punishment. Here's my reasoning...
People may be getting murdered, but if you sentence them to death, you're not giving them a chance to feel remorse, or repent.
You can't stop killing with killing, it's impossible. Not to mention, sometimes when you use capital punishment, it makes citizens think murder is okay when they are the victim of a crime. Example, you have people killing others because those people stole from them, or because they destroyed their property, etc.
I'd say let's put a stop to capital punishment in the US to show that taking another persons life is immoral and stick to the more humane punishments(20 years to life, life, life without parole, etc.)