At Language Log, Arnold Zwicky discusses the recent changes to instructions for California jurors. An article by David Kravets of 25 August goes into some detail. Peter Tiersma was involved – see his website for more materials on language and law.
bq. OLD: “A witness who is willfully false in one material aspect of his or her testimony is to be distrusted in others. You may reject the whole testimony of a witness who willfully has testified falsely as to a material point, unless, from all the evidence, you believe the probability of truth favors his or her testimony in other particulars.”
bq. NEW: “If you decide that a witness deliberately lied about something important, you should consider not believing anything that witness says. Or, if you think the witness lied about some things, but told the truth about others, you may simply accept the part that you think is true and ignore the rest.”
Now I think they had picked that one up before the O.J.Simpson criminal trial