Francisco Hernandez thought his girlfriend was 18. She was 17 years and 9 months, and it took the California Supreme Court to decide whether those three months should cost him a conviction.
Short answer: in most states, a mistake of age defense doesn't exist. Statutory rape is a strict liability crime almost everywhere, meaning the prosecution never has to prove you knew the age, and your honest belief is legally irrelevant to guilt. A minority of states allow a reasonable mistake of age defense, usually through case law rather than statute, and even those states cut it off once the victim is young enough. If your plan is "she told me she was 19," you're relying on an argument most courts won't hear.
I've been writing about criminal defense for 14 years. This is the widest gap between what people assume the law does and what it actually does, and that gap costs defendants badly.
What Does Strict Liability Mean for Statutory Rape Charges?
The prosecution proves two things and stops: the act happened, and the other person was under the age of consent.
No mental state required. No showing you knew, suspected, or should have suspected.
Connecticut's Office of Legislative Research surveyed this and put it plainly: most states hold that proof of intercourse plus proof the victim was below the prohibited age is sufficient for conviction, and the defendant's knowledge of the victim's age is not an element of the offense at all.
That's structural, not technical. In an ordinary criminal case, your mental state is something the state must prove beyond a reasonable doubt, and attacking it is where a lot of defenses live. Strip that element out and the defense loses its usual foothold before the trial even starts.
Speeding works the same way. You don't get to argue you thought the limit was 65.
Which States Allow a Reasonable Mistake of Age Defense?
Fewer than you'd think, and the honest answer is that nobody has a reliable count.
The modern line starts with People v. Hernandez, 61 Cal.2d 529 (1964). The California Supreme Court held that an honest and reasonable belief the partner was of age could defend a statutory rape charge, overruling People v. Ratz from 1896. The court's logic was narrow: the governing statute expressed no legislative intent to impose strict liability, so the ordinary requirement of criminal intent survived.
Some states followed. Some followed and then backed out. Illinois and New Mexico each enacted statutes permitting the defense and later repealed them.
Here's the caveat almost every article on this topic skips. There is no authoritative national list. The Connecticut OLR report flagged that no central source catalogs which states allow the defense by statute, and that secondary sources on the question are confused and contain errors. So when a site tells you confidently that "17 states permit it," that number came from somewhere unverified.
What holds up:
| Jurisdiction | Mistake of age defense | Worth knowing |
|---|---|---|
| California | Limited | Hernandez defense; unavailable when the victim is under 14; age of consent is 18 |
| Texas | Not available for statutory rape | Separate 3-year close-in-age affirmative defense, enacted 2007 |
| New York | Not available for most age-based offenses | Age of consent raised 16 → 17 in 2019; no close-in-age exemption |
| Majority of states | Not available | Strict liability governs |
Does It Help If the Minor Lied or Showed a Fake ID?
Less than it should, and this is the part of the doctrine I'd argue with.
In a strict liability state, deliberate deception by the minor is legally irrelevant to guilt. Not "weighed lightly." Irrelevant. Most states treat the defendant's mistake as immaterial even where the minor intentionally lied about their age.
The evidence still matters. Just not where people expect it to. A fake ID, a dating profile listing an adult birthdate, a screenshot of the minor stating an age — none of that dismisses a charge in a strict liability state, but all of it shapes what a prosecutor offers in negotiation and what a judge does at sentencing. That's a real difference in outcome. It isn't the difference between guilty and not guilty.
The specific mistake I see over and over: someone treats that evidence as a reason to talk to detectives without a lawyer. They believe if they just explain about the fake ID, the whole thing resolves. It doesn't resolve, and now there's a recorded statement confirming the act occurred, which was precisely the element the state needed.
Why Do Courts Keep Such a Harsh Rule?
Two reasons. One is better than the other.
The defensible one is evidentiary. If belief about age were a defense everywhere, every case would become a swearing contest over an unverifiable mental state, and the state would have to disprove it beyond a reasonable doubt. Legislatures answered by putting the risk of being wrong on the adult.
The weaker one is historical. These statutes grew from a body of law originally framed around protecting the chastity of young women, and strict liability came bundled with that framing rather than being designed for modern purposes. Courts inherited the rule and later found contemporary justifications for keeping it.
My position: strict liability is defensible on balance, and the protective purpose is real. I also think states recognizing no exception whatsoever — even for a genuinely deceived defendant, small age gap, documentary proof — have drawn the line further than that purpose requires. Both things are true, and the second one doesn't help you if you're the defendant standing in the first one's shadow.
What Actually Helps If You're Facing This Charge?
Get counsel before you speak to anyone. Then work through these questions in order.
What's the age of consent here, exactly? It ranges from 16 to 18 nationally. Roughly 32 states set it at 16, a handful at 17, and around a dozen at 18. Wyoming and New Mexico both raised theirs from 16 to 17 within the last decade, so even the baseline moves.
Is there a close-in-age exemption? This is a separate question from mistake of age, and people conflate the two constantly. Texas has one. California recognizes the Hernandez defense but has no close-in-age exemption at all, which means a 19-year-old and a 17-year-old is chargeable there regardless of how small the gap looks.
Does my state recognize any mistake of age defense, and what's the cutoff age? Ask for the statute or the case, not a verbal summary.
Then preserve messages, profiles, and ID evidence without altering anything. Altering it turns a bad case into a bad case plus an obstruction charge.
The Position I'd Take
Don't build a defense around "I didn't know." Build it around the age gap, the charging decision, and the negotiation, because in most states those are the levers that actually move.
And hire someone who practices in your county, not just your state. Charging practice in these cases varies enormously between prosecutors' offices inside the same jurisdiction, and that variation will shape your outcome more than any appellate decision will.
General information, not legal advice. Laws vary by state and change over time. Talk to a licensed attorney in your jurisdiction about any specific case.