For the benefit of a quick bit of legal writing I've been asked to do, I looked into specialisation in the EU court system. Do the same judges always appear as rapporteur for the same kinds of cases? This seems like the kind of thing that someone should have studied already, but no example springs to mind. So I just Eur-Lexed all cases that cite Kadi and tallied up the rapporteurs.
In the General Court, there were 17 cases in total, including the original Yusuf and Kadi cases themselves. The oldest 8 of those all have one person in common: Judge Nicholas Forwood. (The oldest 5 don't say who the rapporteur was, but Judge Forwood was on the panel for all of them.) Subsequently, he acted as rapporteur 3 more times for a grand total of 11 out of 17. The current go-to Judge seems to be Judge Irena Pelikánová, who authored the two most recent judgements in Fulmen and HTTS, as well as the two Bank Melli cases back when she was still in the 2nd Chamber. The two remaining judgements are by Judge Soldevila Fragoso (with Judge Pelikánová as Chamber President) and Judge Dittrich, whose judgement in Tay Za was recently overturned on appeal by the Grand Chamber.
...Which brings us to the ECJ. They had 6 cases that cite Kadi. The oldest 3, including Kadi itself, were authored by Judge Timmermans. (The cases even followed him to different Chambers: Hassan and Ayadi was in the 2nd Chamber and M & ors in the 4th.) The most recent 2, Tay Za and PMOI, were by Judge Cunha Rodrigues, with the missing one, the Grand Chamber judgement in Bank Melli, being by Judge Rosas.
Counting them all together gives us 23 judgements by 7 different Judges, with both the General Court and the ECJ showing a tendency to give the Judge who wrote the original judgement the subsequent cases on the same topic as well. This is why in my weekly summaries of Luxembourg case law I try to at least mention the Chamber that gave the judgement (there is usually no space for the name of the Judge Rapporteur), but I wonder whether anyone has every studied this question more systematically.
UPDATE 1: Another tally: out of 13 post-Lisbon competition cases before the ECJ, 5 were handled by Judge Juhász.
UPDATE 2: Another suitably specialised topic is the free movement of Turkish workers. I counted 54 cases before the ECJ over the last 25 years or so. Absolute winner: Luxembourgish Judge Romain Schintgen, who was rapporteur in no fewer than 24 of them during his tenure from 1996-2008. Also pretty good: Judge Cunha Rodrigues (8), Judge Kasel (6, also from Luxembourg), Judge Lindh (4) and the Judge who was the first specialist in this area, Judge Schockweiler (2-5, also from Luxembourg). Together, these five Judges are good for 44-47 of the 54 cases in the sample. Luxembourg alone accounts for 32-33 out of 54, but I'm sure that's a coincidence.
(For Judge Schockweiler it isn't entirely clear in how many cases he acted as rapporteur. Before the early 1990s, ECJ judgements don't specify who the rapporteur was. In that period, however, there are three Grand Chamber cases where Schockweiler was a member, so he probably authored at least some of those judgements.)
UPDATE 3: This week's This Week in Luxembourg has another example: 4 cases on internet piracy all by Judge Malenovský.