Here are the descriptions from both the 1992 and 1997 versions as to the traditional teaching of the church on capital punishment.1992 - 2266 The traditional teaching of the church has acknowledged as well-founded the right and duty of legitimate public authority to punish malefactors by means of penalties commensurate with the gravity of the crime not excluding, in cases of extreme gravity, the death penalty.
*1997 - 2267 The traditional teaching of the Church does not exclude, presupposing full ascertainment of the identity and responsibility of the offender, recourse to the death penalty, **when this is the only practicable way to defend the lives of human beings effectively against the aggressor.
***The two statements are phrased differently but mean exactly the same thing until you get to the part in bold letters. This is the difference between them: the 1997 version contains a restriction on capital punishment that is not contained in the 1992 version.
As you pointed out, there are no references in the 1997 version to any document that supports its description of the church’s teaching, and I’m willing to bet that there are no references because there are no supporting documents. As I said, I can reference a half dozen earlier documents that support the 1992 version, but I have never encountered a single statement supporting the restriction the 1997 version claims exists.
Ender