US patent inventorship criteria are tricky, but “conception” of the invention and “intellectual domination” are more important than reduction to practice.
If multiple people are involved with your invention, one issue that commonly arises is: “who gets listed as inventor or co-inventor, and in what order?”
For academic and scientific papers, there is a common order – the junior person who did most of the work often goes in front, the senior professor or principal investigator who may or may not have done much work goes at the end, and other persons go in the middle as co-authors according to usually unwritten criteria. So long as no one is seriously offended, the co-author list otherwise doesn’t matter too much.
Many inventors begin their careers by writing academic papers, and often make the mistake of thinking that the same rules apply to patents.
However, patents are different. You probably wouldn’t let a friend put his name on the deed to your house unless you want to give him co-ownership. Patents are more like property deeds. In the US, just who is and who isn’t a patent inventor can make a big difference in terms of who ultimately owns the patent. As a result, patents have their own set of rules as to who is and who isn’t considered an inventor.
So what are the rules for inventorship? The USPTO rules are covered by MPEP 2137.01 INVENTORSHIP. These rules were worked out through a number of court cases, and are occasionally a bit fuzzy and open to interpretation. At the risk of oversimplification, the main idea is that the inventor is the person who conceived of the invention, and not necessarily the person (such as a supervisor) who suggested working on the problem, or the person (such as a technician or programmer) who did the hands-on work to reduce the invention to practice (e.g. make a working prototype). In fact, reduction to practice is usually not necessary.
Other considerations, such as the issue of “intellectual domination”, are also important. An inventor who is “intellectually dominating” an invention may still be able to use suggestions from others without making them co-inventors.
Things can get tricky. Sometimes the supervisor’s suggestion is really the key insight behind an invention, making the supervisor an inventor. Similarly, sometimes the person reducing the invention to practice ends up solving unexpected problems, and these solutions form a key part of the invention, making the “technician” an inventor. Here looking at the invention’s claims can help sort things out. Who was responsible for what? Note, however, that claims can change during the examination, and sometimes an inventor can end up being added to an invention, or left on the “cutting room floor” as a result.
In any event, the best time to consider these issues is in advance of filing. It is also important to discuss assignment in advance of filing as well since the usual goal (to satisfy due diligence) is to have 100% of the invention assigned to the same persons or organizations.