One of the great scandals of the rabbinic scene in the late 18th century was the publication by R. Saul Berlin of the work he titled Besamim Rosh. The work was described as a collection of teshuvot from an unpublished manuscript, the bulk of which were authored by the 13th-14th century rishon R. Asher ben Yehiel, known as the Rosh. If it were so, it would have been a very important work indeed, as the Rosh was one of the greatest halakhic decisors of all. Included with the teshuvot was a commentary by Berlin himself, called Kasa De-harsena (much Besamim Rosh information at the Seforim Blog).
Something was fishy about the work, namely that it discussed the most absurd questions one could think of--indeed, it read like a parody of she-'elot u-teshuvot--and its conclusions were often permissive to the point of suspicion.
For example: within its pages was the claim (#200) that a shohet needs to test the sharpness of his knife by running it across his tongue (interestingly enough, to give a sample of how it has influenced and penetrated what might be called popular Orthodox culture--as a child I heard that a shohet indeed must check the knife by running it [carefully, one guesses] over his tongue!]). But this is nothing. Within its pages the question of whether guests are to feast at a wedding held on Tisha B'Av due to extenuating circumstances, namely, if the bride is in immanent danger of being abducted by a nobleman (#174) or whether a one-armed man should wear tephillin shel yad along with the shel rosh on his forehead (#100). One teshuvah has the Rosh--a proud, staunch opponent of secular learning--lauding it to the sky.
Needless to say it was suspected as a forgery right away; Berlin being accused of forging it. Indeed, although the work was defended by his father--a distinguished rabbi--it sealed Berlin's already sullied reputation (having previously published an anonymous work scathingly attacking R. Rephael Cohen of Altona, Hamburg and Wandsbeck who had led the attack on Mendelssohn's Bi'ur). For his part, Berlin maintained that he most certainly did not forge it! However, with no name to his name he died shortly after the affair in London.
Assuming he did in fact forge it, the question is, why? At the time it was widely assumed that he intended the work as a sort of Trojan Horse within the rabbinic camp. Berlin, it was thought, simply meant to critique the supposed casuistry of halakhah by slipping such a work into its canon (even though a lately discovered work by a rishon would hardly be likely to become authoritative). Berlin was an early closet Reformer. A more charitable reading can be found in Talya Fishman's essay "Forging Jewish Memory: Besamim Rosh and the invention of preemancipation Jewish culture" in the Yosef Hayyim Yerushalmi festschrift. While agreeing that he intended it is a kind of critique of rabbinic culture, she suggests that his intent may not have been as radical as it seems, because there was an accepted practice of inventing hypothetical questions in order to author teshuvot, perhaps because "real" shu"t requires a timely response. Theoretical ones can be researched in much greater depth and with more leisure. In other words, perhaps the "Trojan Horse" model was not true; he never intended the work to compromise actual halakhah deciding. Indeed, the wording of the stranger teshuvot is vague and elusive.
Be that as it may, the work seems to have been cited as a normal halakhic source in subsequent shu"t literature--unaccountably so, many would say. (No one ever accused R. Saul Berlin of not "knowing how to learn.") It isn't as if criticism of it went away. Indeed, the author of Avnei Nezer claims that the only thing to do with the Besamim Rosh is to burn it--on Yom Kippur which is on shabbos! But, as Fishman notes, learned rabbis such as R. Ovadya Yosef quote from it, seemingly treating it as a halakhic work. R. Shlomo Yosef Zevin wrote that it was certainly a forgery, but one may learn from the work--but not the man [Berlin]. R. Kook too quoted the Besamim Rosh, being well aware that it was a forgery (see Rabbi Kook's View of the "Besamim Rosh").
Indeed, it was most surpising (interesting? alarming? amusing?) to find the following in R. J. David Bleich's Contemporary Halakhic Problems Vol. I see here ("A related question is discussed by Teshuvot Besamim Rosh, a work of questionable authenticity commonly attributed to Rabbenu Asher. Besamim Rosh, no. 340, questions..." -- and then devotes two pages discussing it).