California Evidence Code 1108: Prior Sex Offenses, Notice, and 352

California Evidence Code section 1108 allows the prosecution, in a case charging a sexual offense, to introduce evidence that the defendant committed other sexual offenses as proof of a propensity to commit that kind of crime. That is a sharp departure from the usual rule in California courts, which forbids using a person’s past conduct to argue they acted the same way again. The statute is settled law, but it comes with notice requirements, a judicial balancing test, and jury instructions that shape when and how the evidence actually reaches the jury.

What Section 1108 Changes

Under Evidence Code 1101, prosecutors generally cannot introduce a defendant’s prior bad acts to suggest the defendant has a criminal character and acted on it during the charged crime. Prior acts can come in for narrower purposes like motive, intent, identity, or absence of mistake, but not to argue the defendant is simply the type of person who commits crimes.¹

Section 1108 flips that default for sexual offense prosecutions. When the current charge is a sexual offense, the prosecution can introduce evidence of other sexual offenses by the defendant for exactly the purpose section 1101 forbids elsewhere: to show propensity, and to invite the jury to infer that someone with that history was more likely to have committed the charged crime.²

Removing the section 1101 barrier is not the same as making the evidence automatically admissible. The judge still has to run the proposed evidence through a separate balancing test before the jury hears it.²

What Counts as a Sexual Offense

Section 1108 defines “sexual offense” broadly, covering crimes under California or federal law in several categories:²

Specific Penal Code violations, including rape, lewd acts with a child, unlawful sexual penetration, sexual battery, annoying or molesting a child, human trafficking for sexual purposes, and various child pornography offenses.
Nonconsensual sexual contact between the defendant’s body or an object and another person’s genitals or anus, or between the defendant’s genitals or anus and any part of another person’s body.
Deriving sexual gratification from inflicting death, injury, or pain on another person.
Attempts or conspiracies to commit any of the above.
Assault with intent to commit a sexual offense under Penal Code 220.

Because the definition reaches both state and federal offenses, a prior allegation or conviction from another jurisdiction can qualify as long as the underlying conduct fits one of these categories.

No Prior Conviction Required

The part that surprises most defendants: the prior sexual offense does not need to have resulted in charges, let alone a conviction. The prosecution can present an uncharged allegation, an investigation that went nowhere, or even conduct the defendant was previously acquitted of. What matters is whether the jury in the current case believes, by a preponderance of the evidence, that the prior act occurred.³

Preponderance means “more likely than not.” That is far lower than the beyond-a-reasonable-doubt standard the prosecution must meet to convict on the current charge. The jury receives a specific instruction explaining the difference and telling them to disregard the prior-act evidence entirely if the lower standard is not met.³

Notice to the Defense Before Trial

The prosecution has to disclose any evidence it plans to introduce under section 1108, including witness statements or a summary of expected testimony.² Timing is governed by Penal Code 1054.7, which sets the deadline at least 30 days before trial.⁴

If the prosecution learns of the evidence inside that 30-day window, disclosure has to happen immediately. The court can also permit later disclosure for good cause.⁴ Thirty days is not much time to investigate an allegation that may be years or decades old, locate witnesses, and build a response, which is why late-disclosure fights are common pretrial.

The Section 352 Balancing Test

Even when the prior conduct fits the statutory definition, the judge is the gatekeeper. Evidence Code 352 lets the court exclude evidence when its probative value is substantially outweighed by the risk of unfair prejudice, jury confusion, or wasted time.⁵ In section 1108 litigation, this is where most of the real fighting happens.

The California Supreme Court set out the factors trial judges should weigh in People v. Falsetta (1999):⁶

How closely the prior offense relates to the charged crime.
How remote in time the prior offense is. There is no fixed cutoff, but older allegations carry less weight.
How certain it is that the defendant actually committed the prior act. A conviction is more certain than an uncorroborated accusation.
How similar the prior conduct is to the charged offense. More similarity means more probative value.
How inflammatory the prior act is compared to the charged one. If the prior conduct is far more disturbing, the jury may convict out of disgust rather than proof.
How difficult it will be for the defense to respond to a long-ago act.
Whether less prejudicial alternatives exist, such as admitting some prior offenses while excluding others, or stripping out inflammatory details.

The Falsetta court also observed that priors ending in actual convictions tend to be less prejudicial than uncharged allegations, since the jury is less tempted to convict in the current case to punish conduct that was never adjudicated. Trial judges get wide discretion under section 352, and appellate courts rarely disturb those rulings. The constitutional challenges to section 1108 itself have failed; the Supreme Court held in Falsetta that the statute’s safeguards satisfy due process.⁶

What the Jury Is Told

When prior-offense evidence comes in under section 1108, the jury gets a limiting instruction. CALCRIM 1191A covers uncharged prior offenses; CALCRIM 1191B covers prior offenses that were separately charged and proven. Either way, the instruction tells jurors three things:³

They may consider the prior-act evidence only if they first find, by a preponderance of the evidence, that the defendant committed the prior act.
If they make that finding, they may (but are not required to) infer that the defendant had a disposition to commit sexual offenses and was therefore more likely to have committed the charged crime.
The prior-act evidence alone is not enough to convict. The prosecution still has to prove every element of the charged offense beyond a reasonable doubt.

That last point is where the law asks a lot of jurors. They are told they can use prior acts to infer propensity, but cannot convict on propensity alone. Holding that line in the deliberation room is hard, which is why defense attorneys concentrate their efforts on keeping the evidence out at the section 352 stage rather than trusting the instruction to contain the damage.

Section 1108 and Section 1109 Are Not the Same

Section 1108 has a companion statute for domestic violence cases. Evidence Code 1109 uses a parallel framework but is limited to domestic violence prosecutions and includes a 10-year presumptive time limit on prior acts, which can be overcome only if admission serves the interest of justice.⁷ Section 1108 contains no statutory time limit of its own. A sexual offense from decades back can be admitted if it survives the Falsetta balancing, with remoteness weighing against admission rather than barring it outright.

1
California Legislative Information. California Evidence Code 1101 – Evidence of Character
2
California Legislative Information. California Evidence Code 1108 – Evidence of Commission of Another Sexual Offense
3
Justia. CALCRIM No. 1191A – Evidence of Uncharged Sex Offense
4
California Legislative Information. California Penal Code 1054.7
5
California Legislative Information. California Evidence Code 352 – Excluding Evidence
6
Justia Law. People v. Falsetta (1999)
7
California Legislative Information. California Evidence Code 1109 – Evidence of Domestic Violence