Supreme Court Justice Elena Kagan’s absence from the bench October 15 during arguments in the closely watched Michigan affirmative action case highlights the fact that three years into her tenure, her prior job as solicitor general is still triggering numerous recusals.

Justice Samuel Alito Jr. has also recused in a significant number of cases already this term, some of which cannot be explained by his stock holdings. An inheritance in 2012 left him with a broader portfolio of stocks in companies involved in cases before the court. But he sold them late last year, making it unlikely that they are the reason for his latest actions.

The court’s other justices also take themselves out of cases from time to time, but not usually in numbers seen with Kagan and Alito. Chief Justice John Roberts Jr. and Justice Sonia Sotomayor, like Alito, still run into cases that were pending in the lower courts where they previously sat as judges. Justice Stephen Breyer also owns stocks and has a policy of recusing in cases handled at an earlier stage by his brother Charles Breyer, a federal district judge in the Northern District of California. None of the justices ordinarily explain why they bow out of a case.

But during Kagan’s tenure as solicitor general in 2009 and 2010, her office considered filing a brief while the Michigan case was pending at the U.S. Court of Appeals for the Sixth Circuit, according to a lawyer involved in the litigation. No brief was filed.

Similarly, Kagan recused in last term’s affirmative action case, Fisher v. University of Texas, in which the SG’s office was involved. The federal recusal statute requires judges to step aside in cases in which they provided advice or counsel or expressed an opinion during prior government service.

The court’s junior justice is also still recusing herself in less-noticed cases as well. The orders list issued by the court on October 7, reporting the disposition of roughly 2,000 petitions filed over the summer, listed 35 cases in which Kagan was recused. On the October 15 orders list, her recusal was noted in five more cases.

Kagan’s recent recusals came in cases in which the court denied review, which has less impact than in cases the court has granted and will decide. In granted cases, with only eight justices sitting, the possibility of a 4-4 tie is real. But even with certiorari denials, the absence of one justice makes it that much harder for the party seeking review to obtain the four votes needed for the court to add the case to its argument docket.

One Kagan recusal announced October 7, for example, came in a case brought by former Newark New Jersey mayor Sharpe James, who was challenging his federal conviction on corruption charges. Kagan also did not participate in the court’s decision to deny review in Palmquist v. Shinseki, the case of a federal employee who claimed he was discriminated against because of a disability.

Kagan also bowed out of Hartman v. Moore, a long-running First Amendment retaliation dispute between a Texas businessman and a group of federal agents that the high court ruled on once before. Chief Justice John Roberts Jr. also recused, likely because the case arose from the U.S. Court of Appeals for the D.C. Circuit, where Roberts was a judge before joining the Supreme Court in 2005.

Kagan is not the first justices to face the problem of stepping aside in cases they reviewed at earlier stages as solicitor general. Thurgood Marshall and Stanley Reed, both former SGs, had the same experience when they joined the Supreme Court.

Cumulatively, Kagan’s continuing recusals make it all the more remarkable that she did not recuse in the cases challenging the Affordable Care Act in 2012. Emails from early 2010 released under the Freedom of Information Act indicated that Kagan was walled off from discussions of the legislation at the earliest stages, perhaps anticipating a future recusal issue.

Some of Justice Alito’s recent recusals are more difficult to interpret. The October 7 list indicated he recused in 15 cases, and three more were noted on October 15.

In EPA v. EME Homer City, a Clean Air Act case that has been granted and will be argued December 10, Alito “took no part” in granting a routine motion. That terminology in an orders list is the signal that a justice is recusing. Alito did not recuse himself in June when the court first granted review in the case, which involves regulation of air pollution that originates in one state and affects other states downwind.

A large number of energy companies are parties to the case. They do not appear to match up to the names of companies in which Alito holds stocks, according to his 2012 financial disclosure form. It is possible, though, that there are connections through subsidiaries or joint operations. It’s also possible that Alito acquired new stocks in 2013. Any new holdings won’t be revealed until next spring, when justices’ 2013 financial disclosure forms are released.

Alito reported in 2012 that he and his wife had holdings in many more companies than in past years, apparently because of the death of his father-in-law Bobby Gene Bomgardner that year. More than a dozen of the new holdings were in energy companies. Alito reported selling the shares in the newly gained stocks before the end of 2012, meaning that he no longer owned them when the petitions the court has acted on this month were first filed.

It is also possible, though unlikely, that Alito recused in the Clean Air Act case because he feels that his energy holdings, even if they are not stocks in named parties, would be affected by the outcome as part of the energy industry in general.

James Sample of Hofstra Law School said that if Alito is recusing because of the general impact of a case on his stock holdings, he is going further than necessary.

“To take an initial stock-based predicate for recusal, and extend it further to an entire field such as cases involving energy companies, even where the particular companies in the cases are in which a Justice does not own stock, seems to me to elevate a purely hypothetical indirect interest at the expense of a very real interest—America’s highly finite resource of only nine active Supreme Court Justices,” said Sample, author of a recent article on the history of Supreme Court recusals.

Sample added that justices “would do themselves, court observers, and the citizenry a real service by providing even cursory explanations for their rationales as to recusals and significant non-recusals.”

Steven Lubet of Northwestern University School of Law, also a judicial ethics expert, said “it would be surprising to see a judge disqualified on the basis of investment in non-party companies, unless the impact of the case would truly be industry-wide.”

“On the other hand,” Lubet continued, “it is always prudent for a judge or justice to recuse when he (or she) believes that his impartiality may be compromised.”

But, Lubet said, it is difficult to know what is behind the recusals because the justices do not give their reasons. “Alas, we are left to guess,” he said. “Thus, we have one more reason that justices should explain their recusals.”

Contact Tony Mauro at tmauro@alm.com.