There has been some talk, after the supreme court recently upheld a ban on partial-birth abortions by a 5-4 majority, that the five Catholic members of the court are making judicial decisions based on their religion. While the argument certainly can be made on its face, there is no evidence that this is true in any real sense. To me, the split in the court is not on religious grounds, but rather on differing interpretations about the scope of privacy allowed by Roe v Wade. To wit, 5 members of the court believe that a ban on partial-birth abortions is allowable under the framework set by Roe, and 4 do not. Nothing more, nothing less. Of course, if you read the opinion, it surely doesn't look that simple (and it isn't), but at the very least the decision was made arguably on constitutional grounds, and any debate is based there, not on religion.
There are certainly some troubling elements in this decision; the fact that at least part of the reasoning is based on the notion that a woman might later regret her decision certainly bears no resemblance to constitutional doctrine. However, to say that the 5 Catholics are toeing the Roman party line makes no sense... The court does not support Rome's just-wage initiative; the court (and in particular its Catholic contingent) is decidely pro-death penalty (which the Church is decidedly against); and the court has upheld the rights of homosexuals to engage in consensual sex. Justice Kennedy (a Catholic) also upheld abortion rights in Planned Parenthood v Casey.
It seems, then, that the recent concern that the nine are allowing their religious convictions rule their decisionmaking is much ado about nothing. Is that to say that the justices are not influenced by their moral or religious convictions? I think it would be foolish to claim otherwise. However, regardless of what I or anyone else thinks of the current members of the court, it's safe to say that they are not agents of Rome, intent upon forcing Catholic doctrine on American jurisprudence. Whatever motivates them, it's far more complex than that.