Section — Slater, Manual of Moral Theology
Section II. Murder of a Consort
Murder by a man and a woman of the spouse of one of them constitutes a diriment impediment to their marriage. This impediment does not arise unless death really ensues; attempted murder is not sufficient. Moreover, the murder must be committed not by one of them alone, even if the other afterward approve of it, but by both, either by mutual physical help, or by moral persuasion of some sort. Death must also be inflicted with the intention of marrying the other when free, as Doctors gather from the end of the law, which is to prevent murder of a consort with a view to marrying someone else. This intention must at least be manifested in some way to the other party, though it is not necessary that it should openly actuate both of them to the perpetration of the crime.
p. ii, 227