Sometimes when judges make new rules they apply retrospectively to cases that have already been decided. Obviously this could cause chaos, so there are limitations that confine the situations in which this retrospectivity can apply. In the United States, as we saw here on 21 February 2008, the rule in Teague v Lane, 489 U.S. 228 (1989) recognises two exceptions to the general rule that decisions do not apply retrospectively: where laws proscribing conduct have been declared unconstitutional, and where new rules concern the fairness of trials. Teague has been applied recently in Chaidez v United States
USSC No 11-820, 20 February 2013.
In Chaidez the appellant sought application to her case of a rule that had been declared by the Supreme Court after the proceedings in her trial had been finalised. The rule is that counsel must advise a non-citizen client of the immigration status implications of a plea of guilty: Padilla v Kentucky, 559 U.S. 356 (2010). Ms Chaidez had not been advised that her permanent residency would be revoked and that she faced mandatory removal as a result of her guilty pleas and convictions for mail fraud charges that were classified as aggravated felonies.
The Court held that the Padilla rule did not apply retrospectively.
This rather surprising result arose from what the majority regarded as the first issue which was whether advice about deportation came within the Sixth Amendment right to counsel. Does the right to counsel include the right to advice about a collateral matter – the consequences of a conviction on immigration status? Before Padilla the states had almost unanimously held that it does not. Padilla created a new rule for most jurisdictions. This new rule did not apply to Ms Chaidez's case because (the opinion of the Court is not clear on this but one can infer the reason) it did not, in terms of Teague, concern the fairness of the criminal proceedings against her.
Sotomayor J, joined by Ginsburg J, dissented. They reasoned that Padilla did not create a new rule but it merely applied the established rule that legal representation must be to a standard consistent with prevailing professional norms (Strickland v Washington, 466 U.S. 668 (1984)). Those norms had developed to require advice about the immigration implications of a guilty plea. Padilla did not apply a direct-or-collateral consequence approach to the Sixth Amendment, and Ms Chaidez's legal representation had fallen short of the required standard.
Outside the United States a retrospectivity issue of the kind that arose in Chaidez would probably be resolved by asking whether the defendant should have been advised of the consequences of conviction, including deportation. The rules of professional conduct should indicate the extent of a lawyer's obligation to advise a client of the consequences of a decision. For example, the Lawyers and Conveyancers Act (Lawyers: Conduct and Client Care) Rules 2008 [NZ], rule 13.13.1:
"When taking instructions from a client, including instructions on a plea and whether or not to give evidence, a defence lawyer must ensure that his or her client is fully informed on all relevant implications of his or her decision and the defence lawyer must then act in accordance with the client's instructions."
A retrospectivity issue would arise if standards had changed so that although advice on immigration status might not reasonably have been required to have been given at the time the client entered a guilty plea, it would be required now. This is an artificial issue here, as it has long been recognised that such advice must be given. But if there had been a change in this, so that "all relevant implications" now include the effect of a conviction on immigration status, would all defendants who had previously entered guilty pleas without that advice now be able to have their convictions quashed and their pleas re-taken?
While it is true that standards of fairness change over time, defendants who are still around to complain of treatment that by current standards was unfair are likely to have a remedy. See Krishna v The State (Trinidad and Tobago)  UKPC 18, discussed here on 12 July 2011.