tion as costs of items omitted by Congress, perhaps inadvertently, from sections 1821 or 1920, witness fees are not an omitted item; they are provided for expressly in both sections. Section 1920 even contains an express provision on expert-witness fees, though not one of which SGE can avail itself. The question for us is not whether Rule 54(d) allows any room for awarding costs not expressly provided for by section 1920, but whether developments since 1932 entitle us to conclude that if the Supreme Court were to revisit the issue of the taxability of expert-witness fees it would overrule Henkel. As neither Farmer nor anything else (as we shall see) gives us reason to think the Court would overrule Henkel if it had a chance to do so, we reaffirm Adams v. Carlson, 521 F.2d 168, 172 (7th Cir.1975), which held (after though without citing Farmer), on the authority of Henkel, that “where, as here, the witnesses involved are expert witnesses, the prevailing party can recover only the statutory amounts prescribed in § 1821 and not additional expert witness fees.” A majority of the other circuits agree. See, e.g., International Woodworkers of America v. Champion Int’l Corp., 790 F.2d 1174 (5th Cir.1986) (en banc); 10 Wright, Miller & Kane, Federal Practice and Procedure § 2678, at pp. 387-88 (2d ed. 1983). (Murphy v. International Union of Operating Engineers, Local 18, 774 F.2d 114, 132-34 (6th Cir.1985), comprehensively discusses the case law on both sides of the question.)
Only our dictum in Illinois v. Sangamo Construction Co., 657 F.2d 855, 865 n. 14 (7th Cir.1981), that “with respect to witness fees, the only recoverable costs under Rule 54(d), except in exceptional circumstances, are those specified in 28 U.S.C. § 1821,” must give us some pause. SGE invites us to read the words “except in exceptional circumstances” as denoting cases where the expert testimony was not just helpful, but necessary, as we may assume it was here. But we prefer to interpret the reference to “exceptional circumstances” as merely a prudent reluctance to shut the door entirely to reimbursing witness fees beyond the boundaries of the statute. Unable to divine the future, judges hesitate to state hard-and-fast rules which foreclose any future appeal to circumstances not foreseen at present. By speaking with caution they do not mean to create exceptions that swallow the rule.
But that would be the consequence if “exceptional circumstances” meant that the expert testimony need only be “necessary” or “crucial” for the expert witness’s fee to be taxable as a cost of suit. Since it is hard to gauge the effect of a particular piece of evidence on a jury, or even on the trial judge in a bench trial, a test of necessity will come down to whether the expert testimony was important to the prevailing party’s case or merely a frill. If the former, then under SGE’s approach the judge must allow the fees of the expert witnesses to be taxed as costs. Expert testimony is required as a matter of law in most cases of malpractice, i.e., of professional negligence. The last time this case was here we held that Fuller had to present expert testimony in order to prove SGE’s negligence, see 719 F.2d at 1346, and this implied that SGE would, as a practical matter, have to present such testimony also, to rebut Fuller’s testimony effectively. And in a great deal of complex litigation, including most patent and antitrust litigation, expert testimony is a practical if not legal necessity. A “necessary” or “crucial” test would create a presumption in favor of taxing the prevailing party’s expert-witness fees to the loser. The extraordinary would become the ordinary.
Such a result cannot be squared with Henkel; and given the magnitude of expert-witness fees in major litigation — in this case they were more than six times greater than all the other items of cost together — it is apparent that by affirming the district court in this case we would be transforming the status of costs, long understood in our system as a relatively minor category of litigation expense except in cases (irrelevant here) where a statute allows attorney’s fees to be taxed as costs. If expert-witness fees can be awarded as costs when the services bought with them