(KANSAS CITY, Mo., AP) — A federal judge has ruled that lawyers for a Missouri couple accused of sexual slavery may call an expert to explain bondage, dominance, sadism and masochism to jurors.

But in his ruling Friday, U.S. District Judge Dean Whipple also said the expert won’t be allowed to discuss whether acts allegedly committed by the couple conform to norms in the BDSM community.

Edward and Marilyn Bagley are charged with keeping a young woman as a sex slave in their home near Lebanon, Mo.

Prosecutors say what might be considered normal for BDSM practitioners is irrelevant in the case. They contend the young woman was tortured without her consent.

But Ed Bagley’s lawyer says jurors will need some understanding of the tenets of BDSM to decide if consent was granted.