What is a troll patent and why are they bad?

By TJ Chiang (Professor at George Mason Law School). Professor Chiang wrote the following squib after reading yet another article complaining about patent trolls.

There is much debate and controversy over the term "patent troll." Let me suggest a fairly narrow definition, but one that identifies a category of patents with distinct problems. Moreover, let me suggest that we should talk about individual patents as "troll patents," rather than entire entities as patent trolls. A troll patent is one that:

  1. Is owned by someone that does not practice the invention.
  2. Is infringed by, and asserted against, non-copiers exclusively or almost exclusively. By copying I mean any kind of derivation, not just slavish replication.
  3. Has no licensees practicing the particular patented invention except for defendants in (2) who took licenses as settlement.
  4. Is asserted against a large industry that is, based on (2), composed of non-copiers.

The problem with a patent troll—or, more accurately, the particular troll patent—that fits all four conditions above is that the troll patent does only two things. First, it gathers dust in the patent office. Second, it inflates prices on products. The patent itself contributes nothing useful to society, in so far as the people who actually make anything useful would have done it equally in the absence of the patent.

These four conditions also rule out a few non-practicing entities; or, rather, many of the patents held by these entities. University-held patents are largely not troll patents, in so far as they are often on substantial advances where the infringers copy. Individual inventors are also not always trolls. An individual inventor that licenses others to commercialize the invention is not a troll; nor where the inventor actually has something significant that gets pirated. But a patent owner who sits in wait to ambush an industry later, with a patent that does nothing otherwise except gather dust, is a troll.

One hypothetical that will surely be thrown at me is the individual inventor who tries to commercialize the invention, but fails, and then sues the industry years later. This inventor is a visionary ahead of his time who was merely unlucky. On the other hand, this inventor still contributed nothing useful to society. It is worth emphasizing the fact that, by my hypothetical, the industry produced the same technology independently, without copying anything from the patent. In the absence of copying by someone else or the commercialization of the product through the patent, I do not see the inventor as having done society much of a favor.