The issue of the value (or the lack of it) of oaths and affirmations in court proceedings came up recently in the High Court of Ireland in ND (Albania) & Ors v The International Protection Appeals Tribunal & Anor  IEHC 451. The applicant and her child had applied unsuccessfully for international protection and appealed to Ireland’s International Protection Appeals Tribunal [IPAT] on 17 August 2018. An oral hearing took place on 5 February 2019 at which the evidence was not taken on oath or affirmation: their appeal was unsuccessful [1-5]. They then appealed the Tribunal’s ruling to the High Court.
The details of the case need not concern us: what is interesting is Richard Humphreys J’s comments at  on the value of oaths and affirmations in legal proceedings, as follows:
“While the challenges of the COVID emergency have necessitated electronic remote hearings involving alternatives to the oath or affirmation, in particular the statement of truth (s. 21 of the Civil Law and Criminal Law (Miscellaneous Provisions) Act 2020), and while the ongoing secularisation of society makes oaths, with their emphasis on religious beliefs, look like a pre-Enlightenment anachronism and an embarrassment, the unfortunate reality is that the oath still has a powerful role in bringing out the truth. There are people who are relatively untroubled about the theoretical civil and criminal consequences of lies to a court or tribunal, but who nonetheless hesitate if asked to call down their deity as a witness to such lies. The rational, bureaucratic, mind fails to appreciate that merely stiffening the criminal penalties for perjury has no effect whatever on that viewpoint. The existence of such witnesses has been illustrated from experience in the IPAT since it began to administer oaths in recent years, and is reinforced by the experience in the Asylum List particularly since the salutary disciplines of Practice Direction HC81 were introduced. Scrapping the oath makes academic sense, but would materially increase the amount of false evidence in practice. Would that it were not so, but it would be wishful thinking to ignore the reality. Overall, the real objection to oaths is that apocryphally attributed to Dr Garrett Fitzgerald: ‘I know it will work very well in practice, but tell me … how will it work in theory?’ (Seamus Martin, ‘Saturday Column’, The Irish Times, 6 July 1985, citing an attribution by Anthony O’Reilly).” [With thanks to Irish Legal News.]
As to whether or not the remark attributed to Dr Fitzgerald is authentic, se non è vero, è ben trovato.