The central point of my present statement is as follows. A friend has pointed out to me today that in a speech of 6 September 2007 on Catholic prisons ministry, Pope Benedict XVI personally endorsed a statement against torture found in the 2005 Vatican Compendium of the Church's Social Teaching. Citing article 404 of this document, the Holy Father said, "In this regard, I reiterate that the prohibition against torture 'cannot be contravened under any circumstances'".You'll have to go and read the whole thing; Father Harrison believes that the question as to whether waterboarding is torture is still an open one, and says that it is unjust to accuse Marc Thiessen of consequentialism (while pointing out that Thiessen makes some particular errors in his arguments).
In my 2005 Living Tradition article on the development of Church teaching regarding torture and corporal punishment (cf. www.rtforum/lt/lt118.html) I had cited and discussed, in my section A13 and footnote 27, this article 404 of the Compendium, which is a publication of the Pontifical Commission for Justice and Peace. I pointed out then that this and other statements authored by the Commission itself - as distinct from the statements of Popes and Councils which it cites abundantly throughout the Compendium - does not possess magisterial authority; for the various Vatican commissions, unlike the Congregation for the Doctrine of the Faith, are not in themselves arms of the Church's magisterium (teaching authority).
However, having now become aware that Pope Benedict himself has personally reiterated this particular statement of the Compendium, I wish to state that I accept the Holy Father's judgement on this matter, and so would not defend any proposal, under any circumstances, to use torture for any purpose whatsoever - not even to gain potentially life-saving information from known terrorists.
There is much to say about Father Harrison's statement, but as he's addressed his letter to Mark Shea, and Mark is presently unable because of other obligations to make a thorough reply, I will refrain from commenting at the present time.