Lord Toulson asked New Zealand's Solicitor-General the $50,000 question in the Privy Council in London this week.
"Why didn't Pora name [Malcolm] Rewa?"
It is a central conundrum in Pora's convictions for the 1992 rape and murder of Susan Burdett.
Pora named a total of five people, all cleared of DNA of being the rapist.
"A very good question," Mike Heron, QC, responded at the two-day hearing of Teina Pora's appeal.
Pora named two gang members in 1993 when a $20,000 reward and indemnity was on offer, then three more names in 1995 from jail when police offered him $50,000 and help with his parole.
Semen from the scene was linked to Rewa in 1996.
Heron was unsure what the jury that convicted Pora in his retrial was told but said it was not hard to think of an explanation, "bearing in mind who Mr Rewa was, his standing in Highway 61".
Yet Pora was unafraid to name some heavy Mongrel Mobsters.
Pora's lawyers' explanation is that Pora couldn't name Rewa because Pora didn't know him and because Pora wasn't there.
Pora cited new evidence - the unreliability of his confessions due to mental impairment, and Rewa's erectile dysfunction - as the basis of his appeal.
The five-member panel of the Judicial Committee of the Privy Council is expected to release its decision in January.