Legal Definitions - common error

A "common error" in copyright law refers to an identical mistake or inaccuracy that appears in both an original, protected work and another work that is suspected of being copied without permission. The presence of the same specific, often peculiar, error in both works serves as compelling evidence that the latter work was not created independently but was, in fact, copied from the former.

Here are some examples to illustrate this concept:

• Historical Text: Imagine a copyrighted history book detailing the life of a relatively obscure historical figure. In one chapter, the author mistakenly states that this figure published their most important essay in 1892, when public records clearly show the correct year was 1893. This specific, unique factual error is present in the copyrighted book. Later, a new biography of the same historical figure is published, and it also incorrectly states that the essay was published in 1892.

  How it illustrates "common error": The unlikelihood of two independent authors making the exact same, specific factual mistake about a less-known detail strongly suggests that the second biography was copied from the first, rather than being the result of independent research.

• Technical Manual: Consider a copyrighted repair manual for a specialized piece of industrial equipment. Due to a drafting oversight, a diagram in the manual incorrectly labels a specific, non-standard bolt as "Part Number Z-42," when the correct part number is "Part Number Z-43," and "Z-42" does not exist for that machine. A competitor later releases their own repair manual for the same equipment, and its diagram also features the bolt incorrectly labeled "Part Number Z-42."

  How it illustrates "common error": Since "Part Number Z-42" is a non-existent or incorrect designation for that component, its identical, erroneous inclusion in both manuals indicates that the competitor's manual likely copied the diagram directly from the original, rather than creating its own accurate technical drawing.

• Fictional Map: A popular fantasy novel includes a copyrighted, intricately drawn map of its fictional world. On this map, a small, invented river is deliberately named "The Serpent's Coil" by the author. However, due to a unique typographical error during the map's creation, it is mistakenly labeled "The Serpent's Soil." Years later, a new fantasy role-playing game is released, set in a world with striking similarities to the novel's. Its accompanying game map also features a river in a similar location, identically mislabeled "The Serpent's Soil."

  How it illustrates "common error": The probability of two independent creators making the exact same, peculiar typo in a fictional place name on a map is extremely low. This shared, specific error provides strong evidence that the game's map was copied from the novel's map.