Finally someone has produced a quantitative measure that tests the ideological biases of supreme court justices, and it shows a good deal of bias. It looks more like a collection of small biases rather than a simple polarization into left and right.
An article titled Alito isn’t “pro-life” or “pro-choice” but “pro-law.” by Jon Adler (who I knew when he was an undergrad and whose opinions I respect) has led me to believe that Alito will be less influenced by his personal biases than the average justice.