Deciding On How Many Independent Claims To Use

Practically every invention can be described in many different ways. The first person to invent a wooden chair, for example, might have focused on the combination of four legs, a seat, and a back, but the same person might alternatively have focused on the use of wood and nails to make a seating device. Since a patent attorney would be charged with trying to protect the invention against all realistic competitors, it behooves the attorney to claim the invention from multiple perspectives.

The standard way of claiming an invention from multiple perspectives is to use a combination of independent claims and dependent claims. The distinction is quite straightforward. Independent claims are those that stand alone, without dependence on any other claim, while dependent claims are those that recite some sort of connection to another claim. In the following example, claims 1 and 6 are all in independent format, while claims 2-6 are all in dependent format:

1. A chair, comprising at least three legs, a seat, and a back, held together with at least one connector.

2. The chair of claim 1, having a fourth leg.

3. The chair of claim 1, wherein the at least one connector comprises a nail.

4. The chair of claim 1 wherein the at least one connector comprises a screw.

5. The chair of claim 4, in which the screw is at least 1 inch long.

6. A chair comprising a wooden frame supporting a seat and a back.

Now, a few observations on these claims. First, claim 1 is always independent. Second, although the claims must be numbered sequentially during prosecution (although there can be gaps caused by withdrawal or abandonment of claims), the dependencies can be set forth in any order. Thus, it is entirely proper for claims 2-4 to be dependent on claim 1, claim 5 to be dependent on claim 2, and claim 6 to be dependent on claim 3. But is it also entirely proper for claim 6 to be dependent on claim 18! Before the patent is actually issued, the patent office will try to renumber the claims in a logical fashion.

Third, a patent can have multiple independent claims. Indeed, some attorneys prefer all their claims to be independent. One advantage is that multiple independent claims make a patent more difficult to dismiss when a competitor's attorney is drafting a non-infringement opinion. That result obtains because dependent claims cannot usually be infringed without the independent claim is also infringed. A patent with only one or two independent claims is also much easier to analyze than a patent with 20 independent claims. Another advantage is that independent claims are typically longer than dependent claims, and those attorneys that justify their charges in part by drafting very long patents appreciate the use of lengthy claims. The attorney can also change terms more readily, calling an item by one name in one claim, and the same item by a different name in another claim. For example, the tip of a catheter may be described as "a tip" in one claim, and as "a tapered portion" in another claim. That distinction might turn out to be useful if the term "tip" were deemed to be overly vague during litigation. Finally, independent claims are relatively easy to draft. The attorney can spend far less mental energy figuring out the logic of which claims should be dependent on which other claims.

Fourth, even though it sounds terrible, the wording of "the at least one connector" in claims 3 and 4 is entirely acceptable. The reason is that the drafter is using the definite article "the" to refer to a specific item for which there is antecedent basis, namely "at least one connector". On the other hand it is usually unnecessary to write in such a stilted manner. It would be much better to initially refer to "a connector" and then later refer to "the connector". The term "a connector" means "at least one connector".