The Third Element: Unauthorised Use, and Whether Detriment Is Needed

In one line

Any use outside the purpose for which the information was given is unauthorised, use need not be conscious, and whether the claimant must also prove detriment is a question Megarry J left open and no court has closed.

What counts as use

The permitted purpose defines the boundary. In Saltman the drawings were given to make tools for the plaintiff; making tools for the defendant was outside it. In Brady the drawings were given for supply of a panel; building a competing machine was outside it. In Seager the idea was disclosed in negotiations for one grip; marketing a grip embodying it was outside it.

So the question is never "did the defendant use the information" in the abstract. It is: for what purpose was it given, and is what he did within that purpose?

Use takes many forms.

• Manufacturing or selling a product that embodies the information.
• Disclosing it to a third party, whether or not the defendant himself gains.
• Using it to compete, for instance approaching the claimant's customers from a list.
• Using it to save time or cost, which is the Saltman "labour and calculation" point.
• Using it in a patent application, which both uses and destroys the secret.
• Using it to negotiate, for example knowing the claimant's costs when bidding against him.

Mere possession is not use, but it is usually the basis for a delivery up order and for a quia timet injunction where use is threatened.

Unconscious and subconscious use

Lord Denning MR in Seager accepted that the defendant's people may have taken the plaintiff's idea without appreciating that they were doing so, their minds having absorbed it during the negotiations. That did not save them.

This is a strong rule and it should be stated in an answer. Liability for breach of confidence does not depend on a dishonest state of mind. A defendant who honestly believes the idea was his own is liable if in fact it came from the claimant.

It also explains a piece of practice. A company that receives an unsolicited idea will often refuse to look at it, or will route it to a team walled off from the relevant developers, precisely because once it has been seen it cannot be unseen and the company cannot later prove independence.

Independent development, and who must prove it

Independent development is a complete answer, because the claimant's information was then not used at all.

But in practice the burden is evidential and it falls on the defendant. Once the claimant shows that the defendant had access to the information and that what the defendant produced closely resembles it, the court will expect the defendant to explain how he got there.