Source Code Review: A Powerful Tool in Technology Patent Infringement Litigations



[author: Devan Holley]*

According to Statista*, in 2020 computer technology patents made up the majority of patent applications in the U.S., totalling approximately 60,000 patents. In 2022, Unified Patents** found that software, hardware, and networking-related litigations constituted approximately 70% of all district court litigations. This surge in technology-related patent applications and litigations underscores how important source code review has become for infringement detection.

Litigators often find that certain features of patent claims, such as software background processes, server-side functionalities, low-level functionalities, etc., cannot be detected through product testing. For such claim features, evidence of software patent infringement can only be detected within the product’s source code. Hence, source code review has emerged as a critical aspect of these types of litigations. Source code review is typically conducted on behalf of the plaintiff to analyze the defendant’s product, but it can also be used by the defendant to find contradictory evidence that disproves the plaintiff’s claims of infringement.

Components of Source Code

The source code is the most fundamental component of a software product. It details all aspects of a software product, including how and where data is stored within it, such as on a local system, server, or database. The source code delineates the data processing, output generation for end-users, and provides details about the storage and usage of variables and parameters in the program. Tracking such details and tracing the flow of control structures and function calls provides an unambiguous understanding of the software’s functionality. Additionally, source code often includes comments and imported library details that provide even further insights into the workings of the software program.

All these details are included in multiple source code files, which contain functions, function definitions, variables, and other data. Examining these files and folder structures provides valuable insights into the high-level functionalities implemented by the source code. During development, these files may go through changes, and the code base may be released in various versions to fix any issues, or “bugs,” and to introduce new features. Git logs provide a timeline of these changes and documents who made what changes to the code and when. Even if older versions are missing, the git logs still provide a full timeline of the software’s code base and development process.

Source Code Review in Action

Consider a hypothetical example where a client has a patent that describes a method used by a mobile photo editing software where the photos taken by a camera are processed and edited on a remote server. Upon capturing an image, the photo file is sent to a server for distinctive processing and then an updated media file is returned to the user for download. These types of features of a patent claim executed at the server-end cannot be identified through product testing. However, a comprehensive source code review of both the application code and server-side code can provide such evidence. Through code review, every step of the software’s operation can be identified, thereby confirming if there is infringement with how the patented features are utilized in the photo editing software.

Source code review provides an inside look of how software products work. It is critical to getting an objective look at how a technology behaves, communicates with other devices, stores data, and executes various operations. Source code findings can be used to compile expert reports, to fill in gaps in the patent infringement contentions, and to develop questions for depositions. Findings from the source code review can deliver the most convincing evidence that proves or disproves infringement, making it pivotal enough to influence the overall case strategy.

*Senior Associate



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