Legal Definitions - substantial-certainty test

The substantial-certainty test is a standard used in copyright law to determine if one creative work has been illegally copied from another. When two works are similar, this test helps a court decide if the similarities are so striking and pervasive that a reasonable person, looking at both works, would be convinced with a high degree of certainty that the second work was indeed copied from the first. It's not about proving identical copying, but rather whether the similarities are so significant and specific that independent creation is highly improbable.

Here are some examples of how the substantial-certainty test might be applied:

• Music Composition: Imagine a popular new song is released by Artist B, and it features a unique, complex guitar riff and a distinctive drum pattern in its chorus. Artist A, a lesser-known musician, claims that Artist B copied these elements from a song Artist A released five years prior. A court would apply the substantial-certainty test by having a "reasonable observer" (perhaps a music expert or even an average listener) compare both songs. If the unique guitar riff and drum pattern are nearly identical in both songs, and especially if they are not common musical tropes, the observer might conclude with substantial certainty that Artist B's song was copied from Artist A's, rather than being an independent creation.

• Architectural Design: A new luxury condominium building is constructed in a city, featuring a highly unusual facade design with a specific arrangement of geometric cutouts and a distinctive roofline. An architect, who had previously submitted a detailed proposal for a similar site with an almost identical unique facade and roofline design, claims copyright infringement. A "reasonable observer" (such as another architect or a design critic) comparing the two designs would apply the substantial-certainty test. If the specific, non-functional, and highly distinctive design elements are replicated in the constructed building, it would likely lead to a conclusion of substantial certainty that the design was copied from the earlier proposal, even if some minor details differ.

• Software Code: A small software development company releases a new mobile application that performs a very specific task, such as optimizing photo storage using a unique compression algorithm. A larger tech company then releases its own app that performs the exact same specific task, and upon examination, independent experts find that significant portions of the underlying source code, particularly the unique compression algorithm and its implementation, are structurally identical or nearly identical to the smaller company's app. A "reasonable observer" (in this case, a software engineer or forensic programmer) comparing the codebases would likely conclude with substantial certainty that the larger company's app copied the unique, non-generic code from the smaller company's original work, as such complex code is highly unlikely to be independently recreated with such precision.