“… to decide whether the decision of the district judge was wrong. What was said in the Celinski case and In re B (A Child) are apposite, even if decided in the context of article 8. In effect, the test is the same here. The appellate court is entitled to stand back and say that a question ought to have been decided differently because the overall evaluation was wrong: crucial factors should have been weighed so significantly differently as to make the decision wrong, such that the appeal in consequence should be allowed.”
“66. … If, as we believe, the correct approach on appeal is one of review, then we think this court should not interfere simply because it takes a different view overall of the value-judgment that the District Judge has made or even the weight that he has attached to one or more individual factors which he took into account in reaching that overall value-judgment. In our judgment, generally speaking and in cases where no question of ‘fresh evidence’ arises on an appeal on ‘proportionality’, a successful challenge can only be mounted if it is demonstrated, on review, that the judge below: (i) misapplied the well established legal principles, or (ii) made a relevant finding of fact that no reasonable judge could have reached on the evidence, which had a material effect on the value-judgment, or (iii) failed to take into account a relevant fact or factor, or took into account an irrelevant fact or factor, or (iv) reached a conclusion overall that was irrational or perverse.”
“93. There is a danger in over-analysis, but I would add this. An appellate judge may conclude that the trial judge’s conclusion on proportionality was (i) the only possible view, (ii) a view which she considers was right, (iii) a view on which she has doubts, but on balance considers was right, (iv) a view which she cannot say was right or wrong, (v) a view on which she has doubts, but on balance considers was wrong, (vi) a view which she considers was wrong, or (vii) a view which is unsupportable. The appeal must be dismissed if the appellate judge’s view is in category (i) to (iv) and allowed if it is in category (vi) or (vii). 94. As to category (iv), there will be a number of cases where an appellate court may think that there is no right answer, in the sense that reasonable judges could differ in their conclusions. As with many evaluative assessments, cases raising an issue on proportionality will include those where the answer is in a grey area, as well as those where the answer is in a black or a white area. An appellate court is much less likely to conclude that category (iv) applies in cases where the trial judge’s decision was not based on his assessment of the witnesses’ reliability or likely future conduct. So far as category (v) is concerned, the appellate judge should think very carefully about the benefit the trial judge had in seeing the witnesses and hearing the evidence, which are factors whose significance depends on the particular case. However, if, after such anxious consideration, an appellate judge adheres to her view that the trial judge’s decision was wrong, then I think that she should allow the appeal.”
“24. The single question therefore for the appellate court is whether or not the district judge made the wrong decision. It is only if the court concludes that the decision was wrong, applying what Lord Neuberger PSC said, as set out above [in Re B at [93]-[94]], that the appeal can be allowed. Findings of fact, especially if evidence has been heard, must ordinarily be respected. In answering the question whether the district judge, in light of those findings of fact, was wrong to decide that extradition was or was not proportionate, the focus must be on the outcome, that is on the decision itself. Although the district judge’s reasons for the proportionality decision must be considered with care, errors and omissions do not of themselves necessarily show that the decision on proportionality itself was wrong.”