Someone who uses a product that infringes a patent does what People Who Know call "direct" infringement. But what about the person who makes the product or sells it to the direct infringer? Does he get off scot-free?

Maybe. It depends on whether the seller "induced" the direct infringer to infringe.

An inducement claim requires that the seller know the patent exists and that "the induced acts constitute infringement." Global-Tech Appliances, Inc. v. SEB S.A., 131 S. Ct. 2060, 2068 (2011).

What the heck does that mean? We know that a good-faith belief that the acts don't infringe the patent — usually because a lawyer opined to that effect – can defeat an inducement claim. You can't know that "the induced acts constitute infringement" if you believe the opposite.

But what if you believe the acts do infringe the patent but that for some reason the patent lacks "validity" — because, say, it doesn't involve patentable subject matter or makes only an "obvious" improvement over prior art?

The Federal Circuit ruled this week that in deciding guilt or innocence under an inducement theory of liability a jury may consider whether the defendant in good faith believed that the patent lacked validity. Commil USA, Inc. v. Cisco Systems, Inc., No. 2012-1042 (Fed. Cir. June 25, 2013).

One of the panel members dissented on that ground. We'll see if the issue goes en banc.