That’s a question I have been asked about the Texas Supreme Court. The answer is, “When you can convince the Court that you are going to add some value that for whatever reason the principal party cannot.”
In federal practice, as discussed more in this post today from SCOTUSblog, the general rule of thumb is that the federal Solicitor General’s office always gets oral argument time when they request it and that private litigants almost never do. (( When state solicitors request divided time, the answer is “sometimes.” States may have an interest in a statute that is meaningful to the Court, as when the State of Texas argued as an amicus in a suit between two private parties asking the Court to find a Texas statute was preempted. ))
In Texas practice, the pattern is a little less clear. When I was at the Texas SG’s office, we would often (but not always) get argument time when we requested it. Private amici seemed to have a harder time getting oral argument time. But, in my experience, they rarely articulated how they could offer value to the Court if they appeared at argument, highlighting the different perspective on the case that they as amicus could bring to the podium.
A major complication for potential amici in Texas practice is Texas Rule of Appellate Procedure 59.6:
59.6. Argument by Amicus Curiae
With leave of court obtained before the argument and with a party’s consent, an amicus may share allotted time with that party. Otherwise, counsel for amicus curiae may not argue.
This sharply limits the Court’s flexibility in accommodating amicus arguments. Each side begins with only 20 minutes of time, and counsel, especially first-time counsel, are often reluctant to yield 5 minutes of time to a helpful amicus. ((This is true even when that amicus is the State. Some litigants would not consent to have the State appear alongside them at oral argument. In federal practice, that would be an unbelievably dumb move. In state practice, it is merely a dumb one.)) What the Court has, on occasion, done is to actually expand the time for argument so that each side has, say, 25 minutes, so that a reluctant party’s counsel would not actually lose any of their time if they consented. Needless to say, this has been a very awkward way to proceed.
The U.S. Supreme Court has the power to divide the time between the party and the amicus as it sees fit. (( In one fairly recent case, the Court actually gave the United States appearing as amicus even more time than it had requested. )) The Texas Supreme Court is more limited in its flexibility. Still, counsel do their clients no favors by being intransigent about keeping an extra 5 minutes of argument time instead of consenting to have a particularly helpful amicus appear alongside them.