Answer:
I do not support the use of the death penalty. If we punish someone who, for example, committed murder by killing them, how are we any better? Murder is murder, no matter what the circumstances are.
Besides that, there have been many cases when people got sentenced to death for crimes they didn't commit. Unlike other sentences, the death sentence can't be reversed. If they got sentenced to life in jail instead, they could've gotten released once the proof of their innocence was found. But with the death penalty that is not a possibility. Murder of an innocent person in such circumstances is no better than the murder someone gets sentenced to death for. And in those cases, no one gets punished for the mistake that cost someone else their life.