What constitutes a defense for purposes of ex post facto analysis?

Further, we note that our high court adopted the Youngblood analysis in Tapia v. Superior Court, supra, 53 Cal.3d 282, 279 Cal.Rptr. 592, 807 P.2d 434. Therefore, it is that analysis which controls the issue of what constitutes a defense for purposes of ex post facto analysis. Further, it must be borne in mind that the word "defense" as it is used before us is a term of art and must be defined according to the context in which it is used. Thus, regardless of procedural or substantive distinctions as they may restrict, abate or bar prosecutions, the term "defense" as used in ex post facto analysis is not defined by its general consequence but rather by its specific application to the crime itself.