Has the Church changed its teaching on capital punishment?

As far as Pope Francis is concerned, yes, it has changed. Under his papal authority Francis said that capital punishment is never allowed, and it has been changed in our catechism. A lot of people are disgruntled about that because of the traditional teaching, and they have every right to be, but that teaching was never made infallible, and therefore the pope could change it. Now, one reason it may be justified is the scientific evidence we have. The system of judge and jury works well sometimes and other times it does not, and someone may be convicted who is not guilty. The most crucial new factor is DNA evidence, which did not exist when the civil codes were written; it only appeared in the 1980s. So far about 265 people convicted in America, most of them for murder, have been exonerated because their DNA was not at the crime scene. That should make any pope think twice about whether the death penalty is the best penalty, because there are other ways to punish. If we lived in a time when there was no way to be certain, then the death penalty would be the best thing we had, but right now it is not. Times have changed, and the Church knows how to move with the times.