At present, the U.S.A. is a “first to invent” nation. In other words, the first person to invent the patentable subject matter is supposed to receive the patent, not necessarily the first person to file a patent application, as is the case in the rest of the world. This may change shortly, but it’s the way things presently work.
For example, let’s take a hypothetical example where a certain someone synthesizes “flubber” on March 20, 2005. He/she then files a US provisional patent application on September 1, 2005. Another person synthesizes flubber on May 5, 2005 and files his/her patent application on May 15, 2005. It is obvious who filed his/her patent application first. But who was the first to invent flubber?
To answer this question, we need evidence. Evidence that would prove that one inventor actually reduced his/her invention to practice before the other inventor. A party must prove priority by clear and convincing evidence if the date of its earliest constructive reduction to practice (filing date) is after the issue date of an involved patent or the publication date of an involved application or patent.
Therefore, it seems to me that it would be very important to keep good records of inventive activities during the time prior to the filing of a patent application. Lab notebooks and other documents may need to be examined in order to determine who is the actual first inventor.
What’s your perspective on the use and value of inventor’s notebooks? Do they add any real strength to an inventor's claims?