1 October 2011Jurisdiction reportsRon Kaminecki

Citations as indicators of prior art

If a patent is found in a prior art search, why not look at the backward citations, those found on the cover of this patent, to see if any could affect the patentability of the invention that is the focus of the search? In doing this, a searcher is using leverage to extract the benefit of the prior art patent’s searchers to at least suggest some other prior art that may not have been found otherwise.

A common problem with backward citations is that the patent applicant may have an ulterior motive for citing certain patents, such as self-citation, thus giving the cited patent more worth than it should have.

A check of the forward citations for a patent may be productive, keeping in mind that the dates of these patents could be after the priority date of the prior art search. But these forward citations do show other applications or uses that may not have been anticipated by the inventors. And the applicant does not have as much control over who is citing a particular patent.

"IF YOU DO FIND EITHER A PATENT OR AN NPL REFERENCE THAT IS CITED BY MANY OTHER PATENT, IT MIGHT BE USEFUL TO INVESTIGATE IT FURTHER TO SEE WHY IT IS SO IMPORTANT TO THE OTHER PATENTS."

But non-patent cited references should not be ignored. These are the citations to items such as conference papers, technical articles, dissertations, book chapters and handbooks amongst other types of literature. They can contain a wealth of information. Not only are such references useful for prior art purposes, they may cover literature that may be impossible to find elsewhere, such as parts catalogues or even court-imposed injunctions!

Again, looking at any cited literature is like reviewing the results of another person’s literature search and while you do not have control over the terms that were used or the thoroughness of the search, you can at least look at the citations to see if there might be any leads that could prove useful.

For example, a cited reference in a patent could refer to a relevant article and the author of this work may now be used as a springboard to find other articles or even patents by this person.

A cited reference to a dissertation could lead not only to many references contained within the work, but could also lead you to a centre of research at the university that awarded the degree. This university could have specialised equipment useful to the invention and could also lead to professors and graduates who may not only have relevant publications, but could be useful as experts or expert witnesses.

Because cited references are not as rigorously checked for formatting as cited patents, sometimes the non-patent literature (NPL) found in this field can be hard to locate in a library. However, a search of other patents could reveal what these missing pieces are and thus give the essential information necessary to order an original.

Do not forget to check the number of times something has been cited. That is not to dismiss items with low citation counts, but if you do find either a patent or an NPL reference that is cited by many other patents, it might be useful to investigate it further to see why it is so important to the other patents. Indeed, the number of citations of a publication has been held to be an indicator of interest not only by patent analysis programs, but by academia itself.

For example, patent EP 200322, by Jens Kristian Perregaard on heterocylic compounds, has been cited more than 170 times and contains almost 50 patent citations, four non-patent literature citations and a 20-member patent family. Looking further into the inventor’s name yields a body of work of 84 publications, but more importantly, more than 200 citations to these works. This single patent yielded several hundred points of reference that could prove to be the essential link to prior art.

Ron Kaminecki is director of the intellectual property segment at Dialog LLC. He can be contacted at ron.kaminecki@dialog.com

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