Impact factors of forensic science and toxicology journals: what do the numbers really mean?

This article presents review and opinion about the use and abuse of journal impact factors for judging the importance and prestige of scientific journals in the field of forensic science and toxicology. The application of impact factors for evaluating the published work of individual scientists is also discussed. The impact factor of a particular journal is calculated by dividing the number of current year citations to a journal's articles that were published in the previous 2 years by the total number of citable items (articles and reviews) published in the same 2-year period. Journal impact factors differ from discipline to discipline and range from 0 for a journal whose articles are not cited in the previous 2 years to 46 for a journal where the average recent article is cited 46 times per year. The impact factor reflects the citation rate of the average article in a journal and not a specific article. Many parameters influence the citation rate of a particular journal's articles and, therefore, its impact factor. These include the visibility and size of the circulation of the journal including availability of electronic formats and options for on-line search and retrieval. Other things to consider are editorial standards especially rapid and effective peer-reviewing and a short time lag between acceptance and appearance in print. The number of self-citations and citation density (the ratio of references to articles) and also the inclusion of many review articles containing hundreds of references to recently published articles will boost the impact factor. Judging the importance of a scientist's work based on the average or median impact factor of the journals used to publish articles is not recommended. Instead an article-by-article citation count should be done, but this involves much more time and effort. Moreover, some weighting factor is necessary to allow for the number of co-authors on each article and the relative positioning of the individual names should also be considered. Authors should submit their research results and manuscripts to journals that are easily available and are read by their peers (the most interested audience) and pay less attention to journal impact factors. To assess the true usefulness of a person's contributions to forensic science and toxicology one needs to look beyond impact factor and citation counts. For example, one might consider whether the articles contained new ideas or innovations that proved useful in routine forensic casework or are widely relied upon in courts of law as proof source. (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.