Same-day audio is also the closest the public can get to a real-time feel for oral arguments. The court has never allowed television cameras to film its arguments, and the current justices have shown no signs of reversing that policy any time soon.

Many observers believe the court is likely to strike down the Defense of Marriage Act, which defines marriage in the eyes of the federal government as a union between one man and one woman. 

Where the justices will fall on the broader question of same-sex marriage is harder to predict.

The California case presents an opportunity to declare that there is a constitutional right to same-sex marriage in every state, if the justices want to go that far. But they also have several narrower options that would leave the issue up to the states.