Does a published patent application end trade-secret protection?

For what it discloses, generally yes. A published application or issued patent is a public document by design, and courts routinely treat information disclosed in one as no longer secret from the publication date. It matters what the document actually discloses: a patent that describes a process in general terms does not necessarily make public the specific parameters a plaintiff claims, so the comparison has to be item by item.

What is the difference between "generally known" and "readily ascertainable"?

Generally known means the information is already common knowledge in the trade. Readily ascertainable means a competent person could find or work it out without undue time or expense by proper means — from public literature, product manuals, published standards, or by reverse engineering a product sold on the open market. The DTSA expressly says reverse engineering and independent derivation are not improper means (18 U.S.C. § 1839(6)(B)).

Is readily ascertainable a defense in California?

California's Uniform Trade Secrets Act defines a trade secret by reference to what is not generally known, and leaves "readily ascertainable" out of the definition (Cal. Civ. Code § 3426.1(d)). California courts have treated ready ascertainability as a defense the defendant raises rather than an element the plaintiff must disprove. In a federal case pleading both the DTSA and California law, the same public documents serve both, but who carries the point differs.

Can a combination of public elements still be a trade secret?

Yes. A plaintiff can claim that a particular combination, selection or sequence is secret even if every component is public. Showing each element in a different document does not by itself answer a combination claim; the stronger evidence is a single document, or a small number of closely related ones, that discloses the combination as claimed. A good report says plainly which claimed combinations it found together and which it did not.

When should the public-domain search be done?

Early. In California, a plaintiff must identify its trade secrets with reasonable particularity before discovery on them (Cal. Code Civ. Proc. § 2019.210), and many federal courts require a comparable identification. The identification is the list the search is run against, and the response to it is where the evidence is most useful. The same documents are used again at summary judgment and in settlement.

Guides

When is a trade secret "readily ascertainable"? The public-domain defense

Michael W. Smith, former USPTO patent examiner · November 1, 2026

Under the Defend Trade Secrets Act, information is a trade secret only if it derives value from not being generally known to, and not being readily ascertainable through proper means by, others who could use it (18 U.S.C. § 1839(3)). If the claimed information was described in a published patent or application, a paper, a manual, a datasheet or a public web page before the alleged misappropriation, the defense can argue it fails that element. The evidence that carries the argument is specific: each claimed secret matched to a public document, quoted, located by page, and dated before the conduct.

What the statute requires

The DTSA defines a trade secret as information the owner has taken reasonable measures to keep secret, and that derives independent economic value from not being generally known to, and not being readily ascertainable through proper means by, another person who could obtain value from it (18 U.S.C. § 1839(3)). Most states follow the Uniform Trade Secrets Act, which uses nearly the same words. Both halves are elements of the claim. The public-domain defense attacks the second: if the information was already public, or could be found with ordinary effort, it was not a secret to take.

Which public documents end secrecy

Source	Why it matters	How it is dated
Patents and published applications	Public by design, often the plaintiff's own, and usually the most detailed description of a process or design	Publication date on the face of the document
Journal papers, theses, conference proceedings	Methods sections describe processes, conditions and results, sometimes by the plaintiff's own staff	Publication or online-first date
Manuals, datasheets, specifications	The most specific public description most products have: parameters, tolerances, configurations	Revision date, or the date the document was first available
Product and company web pages	What the plaintiff or its competitors published about the product at the time	Web archive capture date
Regulatory submissions and standards	Filed disclosures and published standards describe products and methods in detail	Filing, approval or publication date

The date that matters

The information has to have been public before the alleged misappropriation. Many cases have two useful dates: when the defendant first had access (often the start of employment or of a supply or development agreement), and when the alleged misuse began. A document that predates the first date is the strongest evidence; one between the two can still show the information was not secret when it was allegedly misused. A document published after the conduct does not show the information was public at the time, though it may bear on the remedy going forward.

Itemized secrets, itemized evidence

A complaint usually describes the secrets in broad categories. The identification served later lists them item by item, and that list is what the evidence has to answer. The useful format is a chart: each claimed secret in the plaintiff's own words, the public document that describes it, the passage quoted verbatim with its page, the document's date, and an archived copy that can be cited. Items that could not be found in public belong in the same chart, stated as not found, so counsel knows exactly where the case still turns on secrecy.

Where the defense is weakest

Combination secrets. Public components do not make a combination public. Evidence of the combination itself is what answers it.
Specific values. A paper that names the process but not the temperature, ratio or tolerance claimed does not show the value was public.
Customer and pricing information. Business secrets are rarely published. The defense works best for technical secrets: formulas, processes, designs, firmware and specifications.
Reasonable measures. The public-domain defense goes to secrecy, not to whether the plaintiff protected the information. Both elements are usually contested separately.