The term “after-claiming” (also called "late claiming") refers to a patent prosecution strategy in which a patent applicant introduces new claims in a pending patent application after a disclosure or reduction to practice by another party. While the applicant may only claim subject matter that is disclosed in the specification, he or she may capture specific embodiments that are disclosed by others while the application is pending.
For example, if a competitor of the patent applicant were to reduce to practice an invention that is disclosed (but not claimed) by the applicant, the applicant may file an additional set of claims tailored such that the competitor’s product would directly infringe on the new claims.
This is a means by which much of the research that is done with public good funding from the taxpayers or charitable donations can be used to support patent claims that can prevent anyone but the patentee or licensees of the patent from using the technology.
After-claiming is possible because in many jurisdictions, it is possible to introduce new claims at various times throughout the pendency of an application, as long as the subject matter of the new claims was disclosed in the specification as filed.
After-claiming is particularly an issue with “submarine patents”, where a patent application secretly pends for an extended period of time before issuing and becoming available to the public.