Can religious beliefs be used as evidence?

In a recent trial the topic of witness propensity to tell the truth due to their religious and/or lack of religious belief was discussed. To recap, this issue is codified in Evidence Code section 789, which states:

"Evidence of his religious belief or lack thereof is inadmissible to attack or support the credibility of a witness."

We must also recall article 1, section 4 of the California Constitution, which states "[a] person is not incompetent to be a witness or juror because of his or her opinions on religious beliefs."

However, in a civil case, the appellate court held it was proper to show that a witness testifying for a party was of the same religious faith which might tend to bias the witness. Drake v. Dean (1993) 15 C.A. 4th 915. In that case, the court held that Evidence Code 789 does not preclude an inquiry made into a witness's religious beliefs. Section 789 simply codified existing law expressed over a century ago [cite], that evidence relating to whether a witness possesses or lacks religious beliefs is inadmissible on the issue of his credibility as a witness. While one cannot be precluded from testifying because he lacks religious belief, relevant inquiry whether a witness's membership in a particular religious sect or tenet of his faith might tend to bias him is not prohibited. Supra.

It is clear that we cannot dismiss a juror or witness for their religious beliefs or lack thereof. However, despite an interpretation of Evidence Code section 789 to the contrary, the court has in fact permitted lawyers to inquire whether or not a witness's membership to a particular religious sect or tenet might tend to bias him or her.