This article reflects on the author's modest experience as an expert witness in two trials: Osheroff vs. Greenspan (1983), and In the Matter of Baby K (1994). Bioethicists' expertise as scholar-teachers and consultants on particular issues merits qualification by judges as expert witnesses. The article argues that a different kind of expertise – strong moral advocacy – is required to be an effective expert witness. The major lessons of expert witnessing for the author concern the demands and strains on the (...) bioethicist's role as scholar, teacher, and consultant. The Baby K case is analyzed in some detail, due to its importance for bioethics, ethics consultation, and the testimony of bioethicists on either side of the case. Rules of thumb are offered to guide decisions as to choices regarding expert witnessing, as well as a discussion of the interaction of law and bioethics. (shrink)