We’ve all heard the phrase, “You can’t judge a book by its cover.” Well, this adage is especially true when looking at an issued patent as there may be valuable information that is not reflected on its face.
First, printing errors can occur. Late amendments to the claims of the patent (which define the scope of the protected invention) may not make it into the final version of the patent. Thus, the claims that you are looking at may appear broader than they actually are. This is especially important to know when evaluating potential non-infringement positions.
Second, the applicant may have given up significant ground to get its patent granted, which is not necessarily reflected in the patent. For example, the applicant may have distinguished its invention over a prior art system. This could have been done by making claim amendments and arguing their narrow meaning, or by otherwise convincing the U.S. Patent and Trademark Office Examiner that no amendments were necessary because the claims (as written) were sufficiently narrow to get around the prior art. Why is this relevant you ask? Because your company may be practicing a technology that is similar to what the applicant distinguished.
In the end, while you should start with the patent, you should read the back and forth correspondence with the U.S. Patent and Trademark Office (known as the “patent prosecution history”) as mistakes can happen and the scope of the patent may not always be as it appears on its face.