We've finally reached the last of the statutory bars in pre-AIA 102. This last one, 102(g) is the basis for interference practice in the U.S. Basically, if two applications, or an application and a patent exist with almost simultaneous filing dates (within 6 months or so) claiming the same subject matter, that application will be barred under 102(g). This law relates to issues of conception of the invention, reduction to practice and diligence to file.

Conception occurs when the inventor has thought up the idea and realized its potential. Reduction to practice occurs when the idea is made to work. At this stage, no further experimentation is necessary and the invention may actually be used.

Diligence to file is the time between reduction to practice and the filing date of the application. A serious inventor would immediately file his or her application after reducing the invention to practice. Waiting to file is not beneficial and in some cases, the PTO may look upon a long wait (say 3 years, for example) as an abandonment of the application.

An inventor who waits several years to file an application after reducing the invention to practice may lose the rights to the patent to another inventor even if he or she was the first to reduce the invention to practice.