In July this year Judge David Harvey of the North Shore District Court in New Zealand stepped down from the Megaupload extradition case after his comments suggesting that ‘the US is the enemy’ were widely reported. Harvey had been due to preside over a hearing to decide whether to grant a US extradition request for Kim Dotcom and three other Megaupload defendants, who have been indicted for alleged copyright infringement in the US.
A month later, the Florida appeals court ruled that George Zimmerman, the infamous former neighborhood watch volunteer who fatally shot unarmed black teenager Trayvon Martin, should be granted a new judge in his case. Zimmerman’s lawyer, claimed the judge had made ‘gratuitous’ and ‘disparaging remarks’ about Zimmerman and showed bias in a July 5 bond ruling (effectively a bail hearing) raising his bond from $150,000 to $1 million.
In the UK, perhaps the most famous case of alleged judicial bias was the Pinochet case, after the House of Lords ruled in 1998 that the former Chilean dictator had no immunity from arrest and extradition for crimes against humanity. After the judgement, lawyers for Pinochet argued that Lord Hoffman, one of judges in the case, had failed to mention that his wife had worked as an administrative assistant at the human rights group Amnesty International for 20 years and that he himself was involved in a charitable company linked to Amnesty which had made representations in the Pinochet case.
Lord Hoffman denied bias – and indeed one month earlier had decided as part of a 3:2 majority (despite Amnesty opposition) that Trevor Nathaniel Pennerman Fisher, a convicted murdered from the Bahamas, could be executed. However it led to the unprecedented setting aside of the House of Lords judgment, and further delay before Jack Straw decided Pinochet could not be extradited to Spain on medical grounds but should instead be allowed to return to Chile where he died six years later.
So what is the test for apparent judicial bias? At common law it is whether a fair-minded and informed observer, having considered the given facts, would conclude that there was a real possibility of bias. Concretely, would such an observer consider that it was reasonably possible that the judge or tribunal member may be subconsciously biased? Lawal v Northern Spirit  ICR 856 at para 21.
All the cases consistently emphasise that what is in issue is unconscious bias. Judges, like politicians, it seems are incapable of being consciously biased.
‘[The] simple fact that bias is such an insidious thing that, even though a person may in good faith believe that he was acting impartially, his mind may unconsciously be affected by bias.’
R v Gough  AC 646 at 659
‘Bias’ in this sense means that the decision maker ‘might unfairly regard (or have unfairly regarded) with favour, or disfavour, the case of a party to the issue under consideration by him’ or they might be ‘predisposed’ to decide the case or an issue in it in a particular way.
Where a challenge is made then it is for the reviewing court to put itself in the position of such an observer in determining whether the test is made out – Locabail (UK) Ltd v Bayfield Propeities Limited  1 QB 451.
In coming to that conclusion the court will not ‘pay attention to any statement by the judge concerning the impact of any knowledge on his mind or his decision: the insidious nature of bias makes such a statement of little value, and it is for the reviewing court and not the judge whose impartiality is challenged to assess the risk that some illegitimate extraneous consideration may have influenced the decision’ – Locabail para 19.
The grounds on which a real possibility of bias might arise cannot be definitively stated (though it is arguable that any judge who has kept and still insists on putting on the Black cap or who starts twirling around the birch before hearing a case of TV licence avoidance would give unarguable grounds for challenge). However they include the following as summarised in AWG v Morrison  1 WLR 1163:
‘[If]there were personal friendship or animosity between the judge and any member of the public involved in the case; or if the judge were closely acquainted with any member of the public involved in the case, particularly if the credibility of that individual could be significant in the decision of the case … or if, for any other reason, there were real ground for doubting the ability of the judge to ignore extraneous considerations, prejudices and predilections and bring an objective judgment to bear on the issues before him … In most cases, we think, the answer, one way or the other, will be obvious. But if in any case there is real ground for doubt, that doubt should be resolved in favour of recusal.’
If there is apparent bias then the judge or tribunal member must disqualify himself and there is no discretion not to do so. For the purposes of Article 5(4) and Article 6 of the Convention for the Protection of Human Rights, the Court asks whether suspicions of bias are objectively justified in that there is a rational and demonstrable basis for them. As the above quote makes clear prudence should naturally lean on the side of being safe rather than sorry in cases of alleged bias, and matters of inconvenience, costs and delay will be irrelevant where the principle of judicial impartiality is properly invoked.