Well, I'm sure there's a lot of Scripture that allegedly supports Capital Punishment, but I think every interpretation of Scripture depends on how much the interpretator is twisting the words.
Here is the thing that pro-death people don't want to discuss about Romans 13 and Jesus.
Paul: Do not take revenge, my dear friends, but leave room for God's wrath, for it is written: "It is mine to avenge; I will repay," says the Lord. (Romans 12:19)
Clearly, Paul is encouraging us not to take it upon our imperfect and unclean hands to avenge someone but rather allow God, who is perfect and all-knowing, to "repay" what was wronged. Using wisdom, we know it's unwise to let such people free back into society, so rather than taking a life of someone who may even be innocent, locking them up and throwing away the key seems to follow this scripture while simultaneously protecting the rest of society.
Jesus: But go and learn what this means: 'I desire mercy, not sacrifice.' For I have not come to call the righteous, but sinners." (Matthew 9:13)
Jesus: "Let any one of you who is without sin be the first to throw a stone at her." This was when Jesus stopped the execution of the adulterous woman.
Clearly, Jesus believes in love and mercy more than He recognized the government like Romans 13 says. When the government we are suppose to submit to goes against Jesus, why wouldn't we choose Jesus? Jesus is perfect, our government isn't.
Lastly, Romans 13:4 "For the one in authority is God's servant for your good. But if you do wrong, be afraid, for rulers do not bear the sword for no reason. They are God's servants, agents of wrath to bring punishment on the wrongdoer."
Today, we can replace "sword" with "gun". Law enforcement officers, equipped with guns, do in fact arrest "wrongdoers" so they can be brought fourth "punishment" until the guilty. This passage doesn't give authority to cops for shooting any "wrongdoer" though! All Romans 13:4 is saying is that God wants us to recognize the authority the government has over it's citizens.
Once again, did the government not legally execute Jesus Christ? Was he not innocent? God granted authority to Pilot to execute him, this does not mean that Pilot or Judas Iscariot is innocent for sentencing Jesus to die!
When man's laws conflict with God's laws, we as Christians have to recognize and honor God's sovereignty over man's. If believers that believe Romans 13:4 explicitly grants governments authority that express the will of God, then I ask, why be opposed to the US Supreme Court which ruled for marriage equality for all, including homosexuals? Does this principle not go against God's teachings? But you still argue that God ordained the government and we shouldn't ever go against it when it conflicts with what God or Jesus said