Samuel Alito finally joined the U.S. Supreme Court this week after a bruising confirmation battle. He was caricatured by critics as a right-wing automaton who would move in lockstep behind the two most conservative justices, Antonin Scalia and Clarence Thomas.

Yet in his very first vote, the newest justice voted instead with the court's more liberal members to block an execution.

Alito might well end up siding more often than not with Scalia and Thomas during their years together on the bench. But his first vote suggests he will keep an open mind, as he vowed.

It's unfair to make assumptions about decisions from a justice with Alito's record of accomplishments and integrity. It's also foolish, given the unpredictable history of the Supreme Court.