One of the more consequential — and least intuitive — features of California domestic violence law is Evidence Code section 1109. Under this rule, the prosecution can introduce evidence of past acts of domestic violence to help prove that the defendant committed the current alleged act. It does not matter whether the past acts resulted in a conviction. It does not matter whether they were reported to law enforcement. It does not even matter whether they appear in any documentary record. For a defendant in a domestic violence case, this rule changes the evidentiary landscape entirely.

The General Rule and the Exception

California’s general rule on character evidence, contained in Evidence Code section 1101, bars the prosecution from introducing evidence that the defendant committed other crimes simply to argue that the defendant has a propensity to commit crimes. The rule exists because juries, asked to decide whether a specific act occurred on a specific date, are not supposed to convict based on a defendant’s general character or past conduct.

Evidence Code section 1109 is a deliberate exception to that rule, carved out for domestic violence cases. The Legislature concluded that domestic violence has patterns that other crimes do not — that an individual’s history with intimate partners is, in this specific context, relevant to whether a charged act occurred. Section 1109 permits the prosecution to introduce evidence of “other domestic violence” to prove the charged offense, subject to certain limitations. Parallel provisions exist for elder abuse and child abuse cases under the same section.

What Counts as “Other Domestic Violence”

Section 1109 defines “domestic violence” by reference to both Penal Code 13700 (the broader domestic violence definition law enforcement uses) and Family Code 6211 (the Domestic Violence Prevention Act’s definition). Together, these definitions reach a wide range of conduct: physical abuse, attempts at physical abuse, sexual assault, threats, and behavior that has been enjoined under a protective order. The conduct does not have to have produced a visible injury to qualify. It does not have to have been the subject of a police report. It does not have to have resulted in any kind of formal record.

This breadth is one of the rule’s most aggressive features. An alleged victim who testifies about prior incidents — incidents the defendant denies, incidents that produced no witnesses, incidents that were never reported — can introduce that testimony for the jury to consider in evaluating the current charge. The jury is instructed to weigh the credibility of the testimony, but the testimony itself is admissible.

The Ten-Year Window

Section 1109 imposes a time limit that the parallel sexual offense statute (Evidence Code section 1108) does not. Evidence of “other domestic violence” that occurred more than ten years before the charged offense is generally inadmissible. The court has discretion to admit older evidence if the interests of justice require it — for instance, where the defendant’s history shows a consistent pattern that the court concludes the jury should hear — but the ten-year window is the default boundary.

This limit is important strategically. In a defendant with a long history, the defense focuses substantial energy on which incidents fall within the window and which can be excluded. In a defendant whose alleged prior incidents predate the window, the defense argues vigorously that the court should not exercise its discretion to admit them.

Section 352 — The Other Backstop

Even when other-act evidence falls within the ten-year window and satisfies the technical requirements of section 1109, the court can exclude it under Evidence Code section 352 — the broader rule that allows judges to exclude evidence whose probative value is substantially outweighed by the risk of undue prejudice, confusion, or undue consumption of trial time.

The section 352 motion is one of the most important pre-trial motions in a domestic violence case where the prosecution intends to introduce other-act evidence. The defense argues that the proposed evidence is inflammatory, that it would confuse the jury about what they are being asked to decide, that it is duplicative of other evidence, or that the prior incidents are too dissimilar from the current charge to be probative. A successful 352 motion can significantly reshape the prosecution’s case.

The Credibility Problem

The aspect of section 1109 that most concerns experienced defense attorneys is its application to undocumented prior incidents. Because a previous act of domestic violence does not need to be supported by a police report, a medical record, or any external documentation to be admissible, the rule creates space for an alleged victim to introduce testimony about incidents that may not have occurred at all — or that occurred very differently than described.

Defense work on these undocumented incidents typically involves several parallel investigations: locating witnesses who can speak to the alleged time and place, examining contemporaneous communications (text messages, emails, social media posts that contradict the prior-incident account), establishing the defendant’s whereabouts during the alleged prior incidents, and documenting any pattern of changing accounts by the alleged victim. The cross-examination on these prior incidents is often as consequential as the cross-examination on the charged offense.

Common Questions

Does a prior domestic violence arrest that did not result in charges count?

Yes. The fact that the alleged prior incident did not result in formal charges, or that the prosecutor declined to file, does not by itself bar the evidence under section 1109. The defense can argue to the jury that the prior incident was investigated and not prosecuted, but the evidence itself is admissible. This is a difficult feature of the rule for defendants whose criminal history is shorter than their alleged history.

Can the prosecution introduce other-act evidence to prove that the defendant is a “bad person”?

Not directly. The other-act evidence is admitted to help the jury decide whether the defendant committed the current charged act. The jury is given a specific instruction — typically based on CALCRIM 852 — explaining what they may and may not do with the evidence. In practice, the instruction is asked to do a great deal of work, and defense argument on this point is often important at closing.

Does section 1109 apply to elder abuse and child abuse cases?

Yes. Section 1109 contains parallel provisions for elder abuse and child abuse. The mechanics — admissibility of prior acts, 352 balancing, and (for elder abuse) a similar time limitation — function much the same way. The strategic considerations for the defense are similar in structure though specific to the context of each statute.

Can the defense introduce prior incidents of conduct by the alleged victim?

Sometimes, depending on relevance and admissibility rules. Section 1109 is a prosecution-favoring rule, but the broader rules of evidence allow the defense to introduce relevant material — for instance, prior false reports, prior threats by the alleged victim, or patterns relevant to the defense’s theory of the case. The standards and procedure are different from section 1109’s framework, and the defense often makes these arguments in motions filed before trial.

Evidence Code section 1109 is one of the features of California domestic violence law that most often surprises defendants. Effective defense work begins with understanding what the prosecution can and cannot introduce, and with pre-trial motions that shape the evidentiary record before the jury ever sees it. Joseph W. Galasso has defended domestic violence cases in Riverside County for more than 20 years, including extensive section 1109 motion work. To discuss a specific case, schedule a free case evaluation or call (951) 225-4130.