Start With the Patent Claims
Patent infringement is determined by the claims of the patent, not simply by whether two products look alike or perform similar overall functions.
Break the Claim Into Individual Requirements
A patent attorney typically begins by selecting a claim and breaking it into its individual requirements, often called claim limitations.
The attorney then compares each limitation with the accused product or process.
For example, if a claim requires:
- a wheel-speed sensor;
- a controller that determines actual wheel slip;
- the controller also determines a target wheel slip; and
- braking is controlled based on the difference between actual and target slip,
the question is not simply whether the competing vehicle has traction or braking control.
Investigate the Accused Product
Evidence may come from product manuals, technical specifications, schematics, testing, software documentation, source code, physical inspection, competitor patents, regulatory documents, and, after litigation begins, discovery.
Build a Claim Chart
The attorney normally organizes this evidence in a claim chart, with one row for each significant claim limitation.
If even one required limitation is missing, the claim generally is not literally infringed.
In some situations, the doctrine of equivalents may also be considered, but it does not allow meaningful claim requirements simply to be ignored.
The patent's prosecution history is also important. Amendments and arguments made while obtaining the patent can affect how broadly a claim may later be interpreted.
Why Component Relationships Matter
The question is whether the accused system performs each required function in the relationship required by the claim.