California Code, Penal Code - PEN § 1473.5

(a) A writ of habeas corpus also may be prosecuted on the basis that competent and substantial expert testimony relating to intimate partner battering and its effects, within the meaning of Section 1107 of the Evidence Code, was not presented to the trier of fact at the trial court proceedings and is of such substance that, had the competent and substantial expert testimony been presented, there is a reasonable probability, sufficient to undermine confidence in the judgment of conviction or sentence, that the result of the proceedings would have been different.Sections 1260 to 1262, inclusive, apply to the prosecution of a writ of habeas corpus pursuant to this section. As used in this section, “trial court proceedings” means those court proceedings that occur from the time the accusatory pleading is filed until and including judgment and sentence.

(b) This section is limited to violent felonies as specified in subdivision (c) of Section 667.5 that were committed before August 29, 1996, and that resulted in judgments of conviction or sentence after a plea or trial as to which expert testimony admissible pursuant to Section 1107 of the Evidence Code may be probative on the issue of culpability.

(c) A showing that expert testimony relating to intimate partner battering and its effects was presented to the trier of fact is not a bar to granting a petition under this section if that expert testimony was not competent or substantial. The burden of proof is on the petitioner to establish a sufficient showing that competent and substantial expert testimony, of a nature which would be competent using prevailing understanding of intimate partner battering and its effects, was not presented to the trier of fact, and had that evidence been presented, there is a reasonable probability that the result of the proceedings would have been different.

(d) If a petitioner for habeas corpus under this section has previously filed a petition for writ of habeas corpus, it is grounds for denial of the new petition if a court determined on the merits in the prior petition that the omission of expert testimony relating to battered women's syndrome or intimate partner battering and its effects at trial was not prejudicial and did not entitle the petitioner to the writ of habeas corpus.

(e) For purposes of this section, the changes that become effective on January 1, 2005, are not intended to expand the uses or applicability of expert testimony on battering and its effects that were in effect immediately prior to that date in criminal cases.