Last year I was called for jury duty in a federal capital case. I had to go through a rigorous process of filling out an extensive questionnaire (about 30 pages of questions on my religious beliefs, life experiences, education, work history, family background, etc.). Then I was called back to be personally interviewed in the courtroom by the judge, the prosecuting attorney, and the defense attorney. They asked me questions for about an hour. It was definitely the most intensive and personal and exhausting interview I've ever had. I found out later (when I was finally dismissed from service and allowed to read the news again) that I had most likely been released, in the final process of narrowing down the jury, by the defense attorney. I knew that he thought I was too pro-death-penalty because he was the one who spent the most time asking me questions, and they focused mainly on that issue.
I was quite relieved to not have to serve on the actual jury because although I do believe that some crimes warrant capital punishment, I wouldn't want to be the one to have to make the decision to end someone's life. I could do it if I believed it was the right thing to do, but I wouldn't want to be forced into that position.
My experience did give me a better understanding of how the process works, though. It is not something that is taken lightly by anyone involved, including the jury. It takes years for one of these cases to come to trial (so much for swift justice). It takes many months to select a jury, and the judge and the attorneys make as certain as possible that the jurors will consider all of the evidence before reaching a verdict and that none of the jurors are likely to make a snap decision or be unable to stand alone even if everyone else disagrees with them. The jurors are carefully instructed on what it means to find someone guilty beyond a reasonable doubt. If they do find the defendant guilty, then they have to go into the final phase of the trial to decide on the sentence--life in prison or death--based on the aggravating and mitigating factors.
No legal system is perfect, and I know that injustices happen sometimes, but after being involved in the jury-selection process and being instructed on all of the legal things that we were supposed to know to be good jurors, I understand how much effort is involved in trying to ensure a fair trial. I still believe that the death penalty is an appropriate sentence for some crimes, and I uphold the instruction given in Romans 13:
RO 13:1 Everyone must submit himself to the governing authorities, for there is no authority except that which God has established. The authorities that exist have been established by God. 2 Consequently, he who rebels against the authority is rebelling against what God has instituted, and those who do so will bring judgment on themselves. 3 For rulers hold no terror for those who do right, but for those who do wrong. Do you want to be free from fear of the one in authority? Then do what is right and he will commend you. 4 For he is God's servant to do you good. But if you do wrong, be afraid, for he does not bear the sword for nothing. He is God's servant, an agent of wrath to bring punishment on the wrongdoer. 5 Therefore, it is necessary to submit to the authorities, not only because of possible punishment but also because of conscience.