After the Criminal Cases Review Commission had exposed serious police misconduct in the collection of evidence against the accused, the Court of Appeal quashed his conviction for a particularly vile murder. However, while he was serving his sentence and when his conviction was being investigated the defendant made admissions which supported an inference of guilt. The Court of Appeal decided to order a retrial because of this new evidence. That decision was appealed to the Supreme Court.
Were the new admissions tainted by the police misconduct that had led to his conviction and sentence?
The Court split 3-2 on this.
The problem of when events have moved on sufficiently from police misconduct to leave untainted any evidence subsequently discovered often arises in the context of improperly conducted searches. See for examples, R v Wittwer, discussed here on 6 June 2008, Gafgen v Germany, discussed here on 3 July 2008 and again on 25 June 2010, R v Ogertschnig and Police v Chadwick both discussed here on 26 October 2008.
The difference between the judges in Maxwell turned on whether the "but for" test was conclusive: if the admissions would not have been obtained but for the impropriety, they are tainted. Or was this just one matter to be considered in the balance?
You might think it obvious that since Mr Maxwell was in prison serving a sentence that had been imposed as a result of a substantial miscarriage of justice which was of such a magnitude that a stay of proceedings could have been granted () to prevent an abuse of process, his admissions were tainted.
When judges are resisting coming to a conclusion that should be obvious, they tend to call the case a hard one. A cynic might say it wouldn't be hard if they got it right. Lord Dyson repeatedly referred to this case as difficult, and Lord Rodger also noted the Court of Appeal’s difficult decision, Lord Mance didn’t find it an easy case, but Lord Brown dissenting didn’t find it difficult at all (). Lord Rodger acknowledged that he had changed his mind since the hearing; had he not done so, the result of this appeal would have been different.
From this you can guess that the majority held that the admissions were not tainted and that the Court of Appeal had rightly ordered a retrial. Lord Dyson delivered the leading judgment in which he reasoned that the admissions were voluntary and were made in what Mr Maxwell then perceived to be his own interests . So, while they would not have been made but for the tainted proceedings, there were other relevant factors to take into account. Only one  was mentioned here: the seriousness of the offending (but Lord Brown at  adds the strength of the case against the defendant as another). Lord Dyson also accepted that the Court of Appeal was right to think that the admissions were untainted in the sense that the police did not intend to obtain them when they were indulging in the serious misconduct .
This reasoning seems a bit fragile. Lord Dyson also thought that there are two balancing exercises: a narrow one to decide whether there had been an abuse of process, and a wider one to decide whether to require a retrial . But, you might think, a retrial would be pointless if the evidence was inadmissible on abuse of process grounds, and if the abuse was not sufficient to exclude the evidence, how could there be an objection to a retrial? Wasn't Lord Brown right to say  in his dissent that it is really all one question of balancing the conflicting public interests of convicting the guilty on the one hand and maintaining the rule of law and the integrity of the criminal justice system on the other?
The result is fact-specific, and Lord Brown recognised  that if Mr Maxwell had made his admissions after his conviction was overturned there would have been no objection to a retrial.
Lord Collins, also dissenting, added  that a retrial was inappropriate because of the seriousness of the police misconduct, the fact that the admissions would not have been made but for the conviction so procured, and Mr Maxwell had served a substantial sentence.
Well, you can't say it isn't an interesting case. There are some useful summaries of the law on stays of proceedings [13–14], abuse of process [15-16], and of course the interests of justice in relation to deciding whether to order a retrial. The Court did not find it necessary to consider whether the duty to stay proceedings to prevent abuse of process where evidence had been improperly obtained is rightly conceived as a balancing exercise involving the seriousness of the offending: see my discussion of Warren v Attorney-General of the Bailiwick of Jersey on 31 March 2011. Where a stay would, as here, have been appropriate at trial, the court is saying that regardless of whether the defendant is guilty, the official impropriety was so serious that mere exclusion of tainted evidence would be insufficient to uphold the administration of justice. The admissibility decision does take into account the seriousness of the offence, but here the court says the impropriety has outweighed that. In such circumstances, subsequent discovery of new evidence of guilt would be irrelevant. Existing statutory provisions empowering courts to permit retrials of acquitted persons do not apply where stays have been ordered, nor do they require the seriousness of the offence to be taken into account, partly because they only apply to serious offences or to all offences where an acquittal was obtained by the defendant's perversion of the course of justice (obviously I generalise here: check your own statutes).
The misconduct here was indeed something rotten in the state of England. Like the ghost it craved justice but the new day brought new concerns