What is the standard of proof in a civil action where a plaintiff has lost his liberty?

7 We are not unmindful of the symbolic value of the standard of proof recognized in Addington v. Texas, supra, 441 U.S. 418, 99 S.Ct. 1804, 60 L.Ed.2d 323, and do not intend to suggest that loss of liberty for any length of time is equivalent to an ordinary money dispute. However, there is historical precedent for a lesser standard of proof even when liberty interests are at stake. (See, e.g., Pen.Code, 872 (order holding defendant to answer justified by finding of sufficient cause to believe the defendant guilty).)