Over the past day and a half, I’ve been collecting information on the Supreme Court’s permission to appeal (PTA) decisions. I’ve now been collecting them for their own sake – my interest rather lies in whether sitting on the PTA panel makes judges more likely to write a dissent or separate opinion in the resulting judgment.
Nevertheless, the PTA decision is interesting for its own sake. If this were the US, and we were talking about decisions to grant certiorari instead of leave to appeal, we would immediately interpret the decision to grant certiorari in terms of judges’ desire to overturn the appealed decision. I think this line of thinking is unlikely to apply in the UK. Rather, I think the PTA decision may reflect judges’ differing propensities to charitably interpret the appellants’ case, and make it the strongest, most arguable case possible.
I do not think that these differing propensities are a major part of the decision. The PTA documents are full of fairly withering put-downs (“The Court of Appeal was plainly right”). But at the margin, judges’ differing propensities can make the difference.
As a first approximation, let’s look at the percentage success rate by judge: that is, the number of PTA decisions this judge heard which were granted permission to appeal either in whole or in part:
|Judge||Success rate (pct.)||Decisions|
The table shows that most judges are tightly clustered around the average success rate (a little over one-third), but that the gap between the top and bottom judges (seventeen percentage points) seems considerable.
Since, however, these percentages are derived from different numbers of cases, we might wonder how much credence to give to these differences. Perhaps if we were to see more PTA decisions from Lord Toulson, we would find that the next run of decisions would bring greater success for applicants.
To find out whether these differences are statistically significant, we can we can try and model the decision to grant permission to appeal as a function of the judges who sat on the panel. To do so, we use a logistic regression model, which features dummy variables for each judge. Were we to include a dummy variable for each judge, we would not be able to identify their separate effects, and so we have to specify a reference level. Here, I set Clarke of Stone-cum-Ebony as the reference level (though technically he is lumped together with another judge referenced in the March 2011 PTA decisions, one Lord Kirk, who seems neither to be a Senator of the College of Justice nor a LJA).
Alongside dummy variables for the judges, the model includes dummy variables for Scottish and Northern Irish cases, both of which are less likely to be granted appeal.
The results of the model are shown graphically above. The red dots indicate our best guess concerning the effect on the decision of participation by each named judge. Thus, the estimate of 1.2 for Lord Phillips means that a PTA panel with Lord Phillips is 1.2 times more likely to grant permission to appeal than a PTA panel which had Lord Clarke in place of Lord Phillips.
The lines extending to either side of the dot show confidence intervals. Confidence intervals which do not cross the grey line indicate that the relevant judge has an effect which is statistically significantly different from Lord Clarke. Notice that the confidence intervals surrounding Lord Saville are very large, as a result of the relatively few PTA decisions he heard.
From this, we can see that only two judges have effects which are statistically significantly different from Lord Clarke: Lady Hale and Lord Toulson. Generally, comparing across pairs of judges, it is difficult to identify judges for whom the estimates are significantly different.
Three points about these estimates are worth emphasising:
- These estimates can act as a guide to action. If you see that your PTA is being heard by a panel composed of Toulson, Carnwath, and Kerr, advice your client accordingly.
- These estimates may not reveal characteristics of the judges, but only characteristics of the panels with these judges. It’s possible that Lord Toulson is actually very willing to grant PTA, but provokes the opposite reaction in the judges with whom he sits. That is, we are technically committing a fallacy of division here.
- These estimates may not reveal characteristics of the judges, but merely the characteristics of the PTA decisions they hear. Note that the participation of Presidents and Deputy Presidents of the court tends to be associated with a higher success rate. Maybe these judges get assigned the “slam dunk” cases.
I’d be grateful for any other thoughts or caveats which you think worth mentioning.