Example:
You filed a patent application and claimed three structures: A, B, and C. USPTO said that structure C is either anticipated by ref 1 or is obvious over refs 2 & 3. You as the patent practitioner amended the claims to narrow the structures covered to A, B and C' (wherein C' has a smaller scope than C).
Later you found that on the market there was a competitor's product which had structure D. D is either obvious over C or an equivalent thereof, but would not infringe claims under the structure C' in your issued patent. One option you may have is to reissue or reexamine your patent to convert your claims back to A, B, and C. The other is to sue the competitor for infringement in the court. Neither would work because of prosecution history estoppel.
Re-prosecution: USPTO would reject your request to expand the scope of your patent right based on prosecution history estoppel, i.e., you CANNOT re-claim what you have surrendered to USPTO during previous prosecution of your patent if the earlier narrowing amendment were in response to USPTO's patentability rejections. This relinquished IP space has entered the public domain and would not become your private IP property any more. It's gone forever!
Litigation: The Court would not allow you to use doctrine of equivalent to put D as an equivalent of C since you have surrendered your right to own C during the prosecution at USPTO.
The key is that if you has surrendered part of your claims when responding to USPTO's patentability rejections, you cannot retrieve that part (reaction mode). But if you voluntarily narrowed your claims without any threat from USPTO, you may still broaden your claims later on (action mode).
The take-home message is: Be very careful when narrowing your claims in response to a patentability rejection. If you have a chance to argue for the validity of your claims instead of amending the claims, argue in all possible ways you can.
Really simple - if you say your claim is new and inventive over prior art X (or the like), you cannot later claim that your patent is infringed by X
If you want some quick details please see our IPR research page
http://thirdip.com/goss-ip/perusal-prosecution-history-estoppel/
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