Can a priest only consecrate some of the hosts?

[DL82]

As it has been explained to me, during the Mass, the priest only consecrates the amount of bread and wine he intends to. If wine outside the chalices has been left on the altar, this does not become the Precious Blood, because the priest does not intend to consecrate it.

Could a priest who knew that a member of his congregation was in a state of mortal sin, but who also suspected this person would come up to receive Holy Communion, choose to leave one of the hosts in the paten unconsecrated, simply by willing it to be so?

Would this be possible? If so, would it be licit? If not, why not, as the priest in so doing is preventing someone from making a blasphemous communion?

 

[JLASchofield]

This is addressed in De defectibus.
Pope St. Pius V:

1. The intention of consecrating is required. Therefore there is no consecration in the following cases: when a priest does not intend to consecrate but only to make a pretense; when some hosts remain on the altar forgotten by the priest, or when some part of the wine or some host is hidden, since the priest intends to consecrate only what is on the corporal; when a priest has eleven hosts before him and intends to consecrate only ten, without determining which ten he means to consecrate. On the other hand, if he thinks there are ten, but intends to consecrate all that he has before him, then all will be consecrated. For that reason every priest should always have such an intention, namely the intention of consecrating all the hosts that have been Placed on the corporal before him for consecration.

I imagine it would be valid if the priest could determine which host he would give to the person he believes is in Mortal sin and deliberately withhold consecration from that one. However, it is likely this would not be permitted, because the priest at that particular moment does not have the authority to determine whether the person is in Mortal sin, that belongs to the person themselves and their confessor.

 

[Claire_from_DE]

Even if this is possible (which, in theory it might be) it would definitely be illicit. It would be a huge deception, a lie to everyone at that Mass, to only appear to consecrate all the altar bread. It’s impossible to ‘know’ that someone is guilty of mortal sin. Even in the case of a public sinner. And then to appear to give that person communion… What you describe is certainly is not something the priest has a right to do no matter what his motivation is.