The reasoning is necessarily tied to the constitutional jurisprudence on due process, so I just summarise the effect of the decision in terms that may be of more general interest.
Sotomayor J dissented, but the majority held, in a decision delivered by Ginsberg J, that there is no need for a trial judge to have the power to exclude such evidence on grounds other than unfairness to the defence. Irregularities in the conduct of an identification can be the subject of trial remedies, such as confrontation and cross-examination, judicial caution to the jury about the need for care before accepting this evidence, and the judicial discretion to exclude the evidence if its illegitimately prejudicial effect outweighs its probative value.
That is a conservative approach. In our neck of the woods we have radically reformed the law: s 45 of the Evidence Act 2006 imposes a burden of proof of reliability on the prosecution where specified formal procedures have not, without good reason, been followed. The standard of proof here is beyond reasonable doubt. The defence may still challenge the admissibility of the evidence if formal procedures have been followed, but the burden is on the defence to prove on the balance of probabilities that the evidence is unreliable. These provisions are discussed in R v Edmonds [2009] NZCA 303 at [79]-[128] (sorry keen readers, not currently available online). The issue for the judge is whether the evidence is sufficiently reliable to go to the jury, not whether the evidence establishes identity to the relevant standard. Proof of reliability is distinguished from proof of identity, and the focus for the prosecution's burden is on the circumstances in which the identification was made. It does not include other evidence suggesting guilt, such as a confession.
There are issues concerning the interpretation of s 45 that remain to be explored. Its application in judge-alone trials has been considered by the Supreme Court: Harney v Police.
