Conception and Reduction to Practice

In patent law, we often refer to the concepts of “coneption” and “reduction to practice.”  “Conception” refers to “formation in the mind of the inventor, of a definite and permanent idea of the complete and operative invention, as it is thereafter to be applied to practice.”  In other words, conception is the mental act of thinking of the idea of the invention and how it would be implemented. 

“Reduction to practice” refers to the act of actually making the invention work for its intended purpose.  Alternatively, constructive reduction to practice occurs when an inventor files a patent application for the invention.  In some instances, such as the discovery of certain genes or chemicals, an inventor is not able to complete the step of conception until the invention has been reduced to practice.

Some people are surprised that a patent application can constitute constructive reduction to practice; i.e., that a patent application can be filed for an invention that has not be made or actually reduced to practice.  Patent law does not require that an inventor actually make the invention or a model thereof prior to filing a patent application.  In many instances, due to time and financial constraints, it would not be practicable to do so.

Reasons to Develop and Preserve Evidence of Conception

There are a number of important reasons to develop and preserve evidence of this conception.  First, it may be important to prove accurate inventorship in case a question arises at a later date.  In the US, each inventor has an ownership right in a patent application and has the right to license, assign, or transfer his interest in the application without respect to the rights of the other inventors.  This right is often restricted by contract, such as an obligation to assign the invention to an employer.  Inaccurate inventorship may cause a patent to be unenforceable or invalid.

Although there has been some push in the patent reform bills to change the US to a file-to-file (“first inventor to file”) regime, the US, in contrast to much of the rest of the world, a patent is granted to the first person to invent an invention.  If two or more patent applicants file separate patent applications at the PTO for the same invention, the PTO conducts what is called an “interference.”  An interference is basically a mini-trial to determine which inventor invented first and is thus entitled to the patent.  Like trials in court, evidence is what wins the day.  One applicant may have come up with the idea before the other, but if he cannot prove it, he will not win the interference.  That being said, the junior filer (the inventor who files second) in an interference proceeding rarely wins.

The US has a one year grace period for filing a patent application after certain activities, such as sales or public disclosures.  If a patent application is rejected by a prior art reference that is dated within one year of the application’s filing date, the inventor may use evidence of prior conception to remove the reference as prior art to overcome the rejection.  Again, it is important to have such evidence to submit.

There are also certain circumstances when evidence of prior conception may be used to prove non-infringement or invalidity of a patent that one is accused of infringing, such as the prior use defense to an infringement allegation of a business method patent.

How to Develop and Preserve Evidence of Conception

It is important to remember that what counts is what can be proved.

Inventors should keep detailed records of their inventive activity.  This can be in the form of notebooks or other documents and should include as much of the following as possible:

  • facts or circumstances leading to the invention;
  • purpose of the invention or problem the invention is attempting to solve;
  • description of the structure and function of the invention or the steps of any process that comprises the invention;
  • sketches, drawings, pictures, or other graphical details of the invention;
  • any and all known or possible applications of the invention;
  • advantages of the invention over what is already known, perhaps how the invention differs from a competitors product or patent; and
  • any other information that might be relevant to a future proceeding.

The evidence should be signed and dated and preferably witnessed by someone who understands the evidence.  As the invention is further developed and refined, additional evidence should be developed at each step of the process to continue to show conception.

Evidence that is contemporaneously developed is almost always better than evidence that is developed at some later date.  This is because memories fade and documents or other evidence can be lost.  Contemporaneously developed evidence also tends to be more credible because it is not subject to possible taint of a later proceeding.  Courts and the PTO tend to be skeptical of evidence developed for the sole purpose of winning a dispute over the invention.

Evidence of conception will aid a patent attorney in preparing a patent application for the invention, as well as being useful for reasons above.

Reduction to Practice

If a prototype or working model of the invention can be prepared, this will usually aid in preparing and filing a patent application and is certainly evidence of prior invention.  As noted above, however, sometimes it is inpracticable to create such a prototype or model prior to filing a patent application.

An inventor who knows how his invention works should not delay filing a patent application, even if only a provisional application, in order to create a prototype or working model.  Once the conception is complete, any delay can be detrimental to obtaining a valid patent.  A competitor may file an application or additional prior art may be developed in the meantime that may prevent the attainment of a patent.  The clock may begin to run on public disclosure or offers for sale.  And foreign patent rights may be lost.

An inventor may not have the financial resources to prepare a prototype or model.  Often, outside investment is needed to work toward commercialization of an invention.  It is usually advantageous to tell potential investors that a patent application has been filed for the invention.  And there is less risk of the invention being stolen by another party.


The bottom line is that conception is the activity of primary importance in patent law.  Evidence that can be used to prove conception can be very important in the patent process.  Filing a patent application sooner is almost always the best course of action.

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One Response to “Conception and Reduction to Practice”

  1. The Debate Over Proposed Changes to First-to-Invent and the One Year Grace Period « INVENTIVE STEP Says:

    […] invention date is simply too great.  Many junior parties do not even understand how to keep proper records of conception for admission into such proceedings.  Further, interference proceedings are usually like […]

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