|executioner of the Papal States|
The two 'classical' acts of such clarification, the Immaculate Conception and Assumption in many ways were completely unnecessary at the time of their promulgation, except to promote Papal power. The Church had and always will believe the Theotakos was 'full of grace', and had been from her beginning, what the doctrine does is say that Mary's beginning (and therefore our beginning) happened not at birth or at her quickening, or ensoulment but at the moment of conception. The Assumption, with its deliberate ambiguities reconciles the western doctrine of the Assumption and the Eastern doctrine of the Dormition, it purifies the doctrine of possible unnecessary pious legends.
Better uses of infallible teaching are Paul VI's declaration that contraception, (especially/including modern forms of artificial contraception) are contrary to the constant Tradition of the Church. Similarly JPII's, and maybe more clearly Benedict XVI's, declaration that women never have been and therefore never can be ordained priest are the more usual forms of 'infallible teaching' but these statements depend not so much on supernatural inspiration but the Holy See's library and record keeping. I have always thought that amongst the many papal titles ought to be a reference to 'keeper of the archives' or 'first amongst historians'. These are Church teaching because they are historic facts handed on to us, not because a Pope signs a document.
The problem is that if some other historical sources produced contrary historical evidence then 'infallible' teaching becomes very fallible.
So, Pope Francis has declared the death penalty is contrary to the Church's teaching, well the office of executioner to the Holy See has been unfilled for some time now and the Old Testament laid down quite clear rules about about when the death penalty must be enforced, so one can hardly say that the death penalty is historically contrary to Christian doctrine, however one of the strands that has been developed in Catholic theology, really since the declaration of the Immaculate Conception, is that Life, all life, is sacred, that Life is the fundamental right of all human beings.
For the Pope to say that the death penalty is contrary to the constant teaching of the Church is historically untrue. Obviously he can say that the death penalty is contrary to the Church's teaching but that is his opinion and should be taken seriously as he is Supreme Pastor. The problem is that an incoherent Pope or confused Pope damages the whole concept of Papal teaching. What Francis teaches us is to be sceptical about such teaching.