Reverse Engineering and Independent Development: Answering a Trade Secret Claim in California

Last updated: November 2026. Reviewed by Pavel Kolmogorov, California business litigation attorney (State Bar No. 321018).

Reverse engineering means starting with a lawfully obtained product and working backward to learn how it was made. Independent development means reaching the same result through one's own work. Under California law neither one, alone, is an improper means of acquiring a trade secret. (Civ. Code, § 3426.1, subd. (a).) A company accused of copying does not carry the burden of proving its innocence, but it should be ready to show its own development record. Kolmogorov Law, P.C. represents companies accused of misappropriation and companies whose information was taken.

Call (909) 235-6116 or contact us online to discuss a claim that your company copied a design, a process, or a product.

What the statutes say

California's Uniform Trade Secrets Act defines improper means to include theft, bribery, misrepresentation, breach or inducement of a breach of a duty to maintain secrecy, and espionage. Its next sentence is the one that matters here. Reverse engineering or independent derivation alone shall not be considered improper means. (Civ. Code, § 3426.1, subd. (a).)

The federal Defend Trade Secrets Act says the same thing in different words. Improper means does not include reverse engineering, independent derivation, or any other lawful means of acquisition. (18 U.S.C. § 1839(6).)

The idea is older than both statutes. The United States Supreme Court has described trade secret law as offering no protection against discovery by fair and honest means, such as independent invention, accidental disclosure, or reverse engineering. (Kewanee Oil Co. v. Bicron Corp. (1974) 416 U.S. 470, 475-476.) A trade secret is protected against wrongful taking and wrongful use, not against a competitor who got there honestly.

Who has to prove what

These are often called defenses, but in California they are not affirmative defenses. The Court of Appeal has held that the plaintiff carries the burden of proving improper use from the start of trial to the end. Independent derivation and reverse engineering sit inside the definition of improper means. Evidence of either one shows that there was no improper use. (Sargent Fletcher, Inc. v. Able Corp. (2003) 110 Cal.App.4th 1658.)

The same decision carries a warning. Once the plaintiff presents credible evidence of improper use, the burden of producing evidence shifts to the defendant, and a defendant that offers nothing acts at its peril. In that case the jury found that the defendant had access to at least one of the plaintiff's trade secrets, yet found for the defendant on whether it had used them in its own product. The judgment for the defendant was affirmed.

So access does not end the case. Evidence of how the product was built can answer it.

What the word alone leaves out

The statute protects reverse engineering and independent derivation alone, and each has limits.

Reverse engineering starts from a product the company had a right to take apart. A unit bought on the open market, with no restriction on taking it apart, is the plain case. A prototype received under a nondisclosure agreement, an evaluation loan, or a license that forbids disassembly is different. Breach of a duty to maintain secrecy is itself listed as improper means, and the Act leaves contract remedies in place. (Civ. Code, §§ 3426.1, subd. (a), 3426.7, subd. (b).) Our page on breach of an NDA covers the contract claim.

Independent development has to be independent. If someone on the team brought the other company's drawings, files, or test data, the result may no longer be the company's own work, whatever else the team contributed. General skill and experience are a different matter, as our page on what counts as a trade secret explains.

The record that proves independent development

A development story told from memory years later is weaker than a dated record made at the time. These are the records that help.

Version control history, lab notebooks, and design files with their original dates.
Design reviews, test results, and abandoned approaches. Dead ends show that the work was real.
The public sources the team relied on: published papers, standards, supplier data sheets, and products bought for study.
A list of who worked on the project and what each person had access to.
For reverse engineering, the purchase receipt, the teardown notes and photographs, and the names of the people who did the work.

Some companies go further and use a clean team: engineers with no exposure to the other side's information, working from a written specification. No statute requires it. It can make the proof simpler.

How the question comes up

A customer tests a vendor's device under an evaluation agreement, declines to buy, and later releases a device of its own. The questions are what the agreement allowed and whether the customer's design work began before the evaluation.

A young company's founders once worked for an older company in the same field, which now claims the design. The questions are when each feature was conceived and what the founders kept from the earlier job. Our page for a company whose new hire is accused covers the first response to that kind of letter.

A manufacturer buys a rival's product at retail, measures it, and builds a compatible part. If the product was sold without restriction, that is reverse engineering in its plainest form, and trade secret law does not treat it as improper means.

If your company is the one claiming theft

Expect this answer, and prepare for it before filing.

Ask whether the product gives the secret away. Information that anyone can read off a product sold without restriction is hard to protect, as our page on reasonable measures to protect trade secrets explains.
Look for proof of use, not only access: identical errors, the same undocumented choices, or a development time too short to be believed.
Check the contracts. A nondisclosure or no-reverse-engineering clause can support a contract claim that does not depend on trade secret status.
Be ready to identify the secret with reasonable particularity before discovery relating to it begins. Our page on identifying trade secrets explains that step.

What to bring to the first meeting

The letter or complaint, and every agreement between the two companies.
A timeline of the product's development, with the documents that support each date.
The names of the people who worked on it and where each worked before.
For a product that was taken apart: how and when it was obtained.
Anything received from the other company, and under what terms.

Frequently asked questions

A competitor says we stole their design, but our engineers built ours from scratch. How do we prove that?

With records made while the work was being done. In California the competitor has the burden of proving improper acquisition or use, and independent development is not an affirmative defense the accused company must establish. Dated design files, version history, test results, and a list of who worked on the project are what answer the claim in practice.

Is reverse engineering legal in California?

Reverse engineering alone is not an improper means of acquiring a trade secret under Civil Code section 3426.1. A California company may study a product it obtained lawfully and without a restriction on doing so. A contract that forbids reverse engineering, or a product obtained under a duty of confidence, changes the analysis.

Is independent development a defense to trade secret misappropriation?

Yes, in the sense that a company that developed the information itself did not acquire it by improper means. California's Court of Appeal has held that it is not an affirmative defense, because the plaintiff must prove improper use throughout. Once the plaintiff offers credible evidence, though, a defendant that produces nothing in response risks losing.

We bought a competitor's product and took it apart to see how it works. Can they sue us for trade secret theft?

They can sue, but reverse engineering alone is not improper means under California Civil Code section 3426.1, and the federal statute excludes it as well. Keep the receipt and the teardown records. The answer may differ if the purchase came with a license that barred disassembly, or if confidential documents were used along the way.

Does having access to a trade secret prove we used it?

No. In one California appellate case the jury found that the defendant had access to at least one of the plaintiff's trade secrets. It still found for the defendant on use, and the defense judgment was affirmed. Access makes the plaintiff's case easier to start. The defendant's development record is what answers it.

Talk to a California trade secret attorney

If your company is accused of copying, or you believe a competitor's product came from your information, call (909) 235-6116 or contact us online. Kolmogorov Law, P.C. is located in Irvine, California. See also our trade secret attorney page.

This page provides general information about California and federal law and is not legal advice. Outcomes depend on the development record, the contracts, the facts, and the court.