Written description, enablement and claims (35 U.S.C. 112)

Section 112 governs what the specification must teach and how claims must be written. During examination, claims receive their broadest reasonable interpretation, and amendments cannot add new matter.

Patentability: 101, 102, 103 and 1122 min read4 sections

Must-know for the exam

112(a) has three separate requirements: written description, enablement and best mode (MPEP 2161)
Written description shows possession; a functional genus needs representative species or common structure (MPEP 2163)
Enablement is judged by the Wands factors as of the effective filing date (MPEP 2164.01(a), 2164.05(a))
Best mode is the inventor's subjective view at filing; it remains in 112(a) after the AIA (MPEP 2165)
Claims get their broadest reasonable interpretation in light of the specification; embodiments are not read in (MPEP 2111)
'Comprising' is open; 'consisting of' is closed; 'consisting essentially of' excludes what materially affects the basic and novel characteristics (MPEP 2111.03)
Terms of degree are definite if the specification gives a standard (MPEP 2173.05(b))
Trademarks used to identify a material can make a claim indefinite (MPEP 2173.05(u))
'Means for' plus function without structure invokes 112(f); computer functions need a disclosed algorithm (MPEP 2181)
A dependent claim that does not further limit its parent violates 112(d) (MPEP 608.01(n))
New matter added by amendment is objected to; claims relying on it are rejected under 112(a) (MPEP 2163.06)
Product-by-process claims are judged by the product (MPEP 2113)

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Traps that cost marks

Applying the 'consisting essentially of' test to a 'consisting of' claim.
Mixing up the enablement factors with the obviousness considerations.
Thinking a disclosed species supports any genus that contains it.
Accepting 'a processor' as the structure for any computer function.
Treating any claim that refers back as a valid dependent claim.
Treating 'such as' as harmless illustration inside a claim.
Arguing a new process makes an old product patentable.
Believing the AIA abolished best mode.

Description and enablement

Written description asks whether the inventor had possession of what is claimed; enablement asks whether a skilled person could make and use it without undue experimentation. A claim can be enabled but undescribed, or described but not enabled.

•Wands factors: breadth, nature of the invention, state of the art, level of skill, predictability, direction given, working examples, quantity of experimentation.

Claim form

Watch for antecedent basis, exemplary language ('such as'), negative limitations without support, and multiple dependent claims that depend on other multiple dependent claims. For 112(f) limitations, the corresponding structure must be clearly linked in the specification; cure a missing link by amendment without new matter.

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