LEVIN H. CAMPBELL, Circuit Judge.

Bernard Lamoureux, an activist in the Teamsters' two unsuccessful campaigns to organize Wright Line's employees, was discharged from his job as a shop inspector, ostensibly because he submitted an inaccurate record of the times at which he performed inspections on December 29, 1977. Upon Lamoureux's complaint, the Board found that Wright Line had discharged him because of his union activity, in violation of section 8(a)(3) of the National Labor Relations Act. The Board ordered Wright Line to reinstate Lamoureux with back pay. We enforce the Board's order.

I.

Wright Line manufactures computer storage products to the specifications of customers, including government agencies. Lamoureux began working for Wright Line in 1966 and, with the exception of a period between 1971 and 1973, was employed there continuously until his discharge on December 30, 1977. The Board found, with substantial record support, that Lamoureux's work, throughout this period until December 29, 1977 was satisfactory or better. For the last two years of his employment, he worked in the company's Inspection Department, inspecting completed parts for quality and conformity to specifications. This position required that he keep records on two forms: the Inspection Report, which stayed with the blueprint for the inspected part, and the Daily Activity Sheet, on which he recorded the time of each inspection and which he submitted to his supervisor after each day's work.

In 1976, Lamoureux contacted Teamsters Local 170 and initiated an organizational drive among Wright Line's employees. The Board supportably found that Lamoureux was visibly active in the union campaign. An election was held on August 27, 1976, and Lamoureux served as an alternative observer for the union, which lost the election. A second campaign was conducted in the fall of 1977, and Lamoureux was again active. An election was held on October 20, 1977; the union lost again. The Board supportably found that Wright Line management conducted an aggressive (although not necessarily unlawful) campaign against the union, and that management was well aware of Lamoureux's activism, certain supervisors having made "gratuitous remarks" to him about it.

The Board found, on the basis of substantial evidence, that Lamoureux's discharge occurred as follows: on the morning of December 29, 1977, Plant Superintendent Southard asked Supervisor Forte to check on Lamoureux, reporting that he had seen Lamoureux entering the men's room carrying a newspaper. Forte went to Lamoureux's two assigned departments and walked between them until Lamoureux appeared some 35 minutes later. Forte then returned to his office, saying nothing to Lamoureux, and noted the times of Lamoureux's absence. Forte had made no attempt to locate Lamoureux's neither looking in the men's room nor using the plant's page system, although Lamoureux's job included several tasks which would require him to leave his departments for short periods. Later the same day, Forte had occasion to be in Lamoureux's department and did not find him there. About 30 minutes later he found Lamoureux at a workbench inspecting a part. Forte again made a record of the incident but did not ask Lamoureux to explain.

The next morning, Forte checked Lamoureux's Daily Activity Sheet and noted Lamoureux's report that he had made several inspections during the time when Forte had failed to find him in his departments. Forte presented this information to his own supervisor, who stated that this indicated a "dischargeable offense." The two consulted higher officials, who told them that they "could discharge" Lamoureux if his account substantiated the charge. Forte prepared a written report of the incident, had Lamoureux's final paycheck prepared, and then summoned Lamoureux to a meeting with himself and two others. Confronted with the charge, Lamoureux admitted that "the times weren't accurate and they never were," stating that "if you want them right to the second, I can put them right to the second," and asserting that the real reason for the confrontation was his union activity. The supervisors denied this charge and discharged Lamoureux, saying that they no longer considered him trustworthy.

II.

Section 8(a)(3) of the National Labor Relations Act, 29 U.S.C. § 158(a)(3), provides that,

(a) It shall be an unfair labor practice for an employer

(3) by discrimination in regard to hire or tenure of employment or any term or condition of employment to encourage or discourage membership in any labor organization.

This provision is supplemented by section 10(c) of the Act, 29 U.S.C. § 160(c), which authorizes the Board to take remedial action, with the following limitation:

No order of the Board shall require the reinstatement of any individual as an employee who has been suspended or discharged, or the payment to him of any backpay, if such individual was suspended or discharged for cause.

Section 8(a)(3) imposes a prohibition on employers which is simple to state but often difficult to apply in practice: they may not discharge an employee because of his union activity; but they may and should apply their usual rules and disciplinary standards to a union activist just as they would to any other employee. Hence, in a given discharge case it must be decided whether the employer acted because of the employee's union affiliation, or whether he acted because of some factor unrelated to the employee's union status. Local 357, International Brotherhood of Teamsters v. NLRB, 365 U.S. 667, 675, 81 S.Ct. 835, 839, 6 L.Ed.2d 11 (1961) (test is "true purpose" or "real motive").

Often, of course, there are competing explanations of why an employee was fired. Board counsel will point to evidence of anti-union motivation. The employer will cite some instance of misconduct and will deny having been motivated by any other consideration. In such a situation, the Board needs to determine not only whether the asserted misconduct occurred, but whether, even so, it effectively produced the discharge. The employer will doubtless lose if the asserted misconduct is shown not to have occurred. But suppose it occurred? In such event, Board counsel will argue that it was insufficient cause for discharge — that a non-activist would have been retained notwithstanding the offense. The employer, on the other hand, will deny this, and will insist, moreover, on his right, as the employer, to determine what conduct is or is not acceptable.

The Board's approach to these cases — sometimes, although without complete accuracy, termed "mixed motive" cases — has been the source of a continuing controversy among the circuits and between the Board and this court. In the present case, the Board has taken a new approach. Relying on Mt. Healthy City School District Board of Education v. Doyle, 429 U.S. 274, 97 S.Ct. 568, 50 L.Ed.2d 471 (1977), and precedent from this circuit, the Board announced the following rule: general counsel must first "make a prima facie showing sufficient to support the inference that [the employer's opposition to] protected conduct was a 'motivating factor' in the employer's [discharge] decision. Once this is established, the burden will shift to the employer to demonstrate that the same action would have taken place even in the absence of the protected conduct." 251 NLRB No. 150, at 20-21. Applying that test here, the Board found that the prima facie case had been made and that Wright Line failed to prove that it would have taken the same action regardless of Lamoureux's union activity. Wright Line challenges the Board's new approach and its application here as contrary to the provisions of the statute and beyond the powers of the Board in that it places the burden of persuasion on the employer. We are thus called upon to pass on the validity of the Board's new rule as well as on its application to this record.

We start by observing that the Board's new rule seems better than its old one. Previously the Board would find a violation of section 8(a)(3) and order reinstatement whenever it concluded that the discharge was even partially motivated by opposition to union membership. Under this approach, a discharge was improper even if it would have occurred absent the illegal motivation, e. g., the employee may have committed an infraction so serious that any employee — union or non-union — would have been fired. This partial motivation test — as the Board now acknowledges — placed "the union activist in an almost impregnable position once [anti-]union animus has been established." Activists could not be discharged for conduct that would be unforgivable in the case of another employee. The result was to immunize union activists against legitimate discipline for genuine offenses and to deprive employers of the freedom to apply their own rules uniformly to all their employees. See NLRB v. Wilson Freight Co., 604 F.2d 712 (1st Cir. 1979); NLRB v. Eastern Smelting Refining Corp., 598 F.2d 666 (1st Cir. 1979); Liberty Mutual Insurance Co. v. NLRB, 592 F.2d 595 (1st Cir. 1979); Hubbard Regional Hospital v. NLRB, 579 F.2d 1251 (1st Cir. 1978); NLRB v. Rich's of Plymouth, Inc., 578 F.2d 880 (1st. Cir. 1978); Stone Webster Engineering Co. v. NLRB, 536 F.2d 461 (1st Cir. 1976); NLRB v. Fibers International Corp., 439 F.2d 1311 (1st Cir. 1971); NLRB v. Billen Shoe Co., 397 F.2d 801 (1st Cir. 1968); NLRB v. Lowell Sun Publishing Co., 320 F.2d 835 (1st Cir. 1963).

In response to the Board's handling of these cases, we have repeatedly urged the Board to go beyond the employer's obvious wish to be rid of an activist and to inquire into the question of actual cause, giving serious consideration to the employer's legitimate business reasons for discharging the employee. See, e. g., NLRB v. Lowell Sun, 320 F.2d at 841 (Aldrich, J., concurring) (employer's knowledge that discharge will have pleasing result not to be confused with actuating motive). We have expressed this concern by insisting that the Board find the protected activity to be the "dominant motive" for the discharge. See, e. g., NLRB v. Fibers International, 439 F.2d 1311; NLRB v. Lowell Sun, 320 F.2d 835 (Aldrich, J., concurring); NLRB v. Whitin Machine Works, 204 F.2d 883, 885 (1st Cir. 1953) (reinstatement warranted if protected activity "weighed more heavily" than other factors); and cases cited in these opinions. Elaborating on the meaning of this test, we have held that the Board may order reinstatement only after finding that the discharge would not have occurred in the absence of the protected activity. NLRB v. Fibers International, 439 F.2d at 1312 n. 1 1315.

The Supreme Court's decision in Mt. Healthy v. Doyle, 429 U.S. 274, 97 S.Ct. 568, 50 L.Ed.2d 471, followed by Givhan v. Western Line Consolidated School District, 439 U.S. 410, 99 S.Ct. 693, 58 L.Ed.2d 619 (1979), seemed to us to lend strong support to our analysis in the Fibers International case. In cases since Mt. Healthy, we have relied on its expression of the "but for" standard, abandoning our earlier "dominant motive" language. Statler Industries, Inc. v. NLRB, 644 F.2d 902 (1st Cir. 1981); NLRB v. Eastern Smelting Refining Corp., 598 F.2d 666, 671 (1st Cir. 1979); Coletti's Furniture, Inc. v. NLRB, 550 F.2d 1292 (1st Cir. 1977). We came to recognize that the existence or not of a causal link between union activity and the employee's injury — or, as section 8(a)(3) puts it, the existence of antiunion "discrimination in regard to hire or tenure of employment" — was most accurately determined by asking whether the discharge would have occurred "but for" the protected activity. If the discharge would have occurred absent the protected activity, it is clear no unfair practice existed since a bad motive without effect is no more an unfair labor practice than an unexecuted evil intent is a crime. While Mt. Healthy involved employee activity protected by the Constitution rather than by the NLRA, it presented issues of causation, harm and remedy very similar to those raised in the labor context, and the Court expressed the same concerns that we have voiced in labor cases. The lower court in Mt. Healthy, like the Board in past labor cases, had ordered reinstatement on a finding that the protected activity was one of two reasons for the decision to discharge the employee. The Court's dissatisfaction with this result was exactly what ours had been: that the employee who engaged in protected conduct would thereby be placed in a better position than he would have held if he had not done so, and his employer's freedom to apply legitimate performance standards would be impaired by the activist's favored position. Id., 429 U.S. at 285-87, 97 S.Ct. at 575-76. To avoid these results while protecting the employee's rights, the Court ruled that reinstatement should be ordered only upon a finding that the employee would not have been discharged but for the protected conduct. In labor cases, as in constitutional cases, we think the "but for" test is the correct substantive standard for evaluating the propriety of a reinstatement order.

Wright Line does not appear to quarrel with this substantive test. Its challenge is to the Board's apparent adoption of Mt. Healthy's allocation of the burdens of proof. Mt. Healthy held that once the plaintiff had shown his protected activity to have been a "substantial" or "motivating" factor, "the court should have gone on to determine whether the Board [of Education] had shown by a preponderance of the evidence that it would have reached the same decision as to respondent's reemployment even in the absence of the protected conduct." Id., 429 U.S. at 287, 97 S.Ct. at 576. See also Givhan v. Western Line, 439 U.S. at 416, 99 S.Ct. at 697. Wright Line contends, citing section 10(c) of the National Labor Relations Act, the Board's regulation 101.10(b), and section 7(c) of the Administrative Procedure Act, that the Board lacks authority to place any burden of proof on the employer. Wright Line argues that these provisions require the Board to prove the employer's guilt by a preponderance of the evidence, and that the Board's burden-shifting approach instead requires the employer to prove his innocence.

We have no difficulty accepting the Board's formulation that some kind of a "burden" devolves upon the employer once the general counsel has made a prima facie showing that protected conduct was a motivating or substantial factor in the discharge decision. 251 NLRB No. 150, at 20-21. Indeed, in Statler Industries v. NLRB, this court approved the general causation analysis expressed in the Board's Wright Line opinion. 644 F.2d at 905. On further reflection, however, we disagree with the Board on the narrow issue of defining the exact nature of the burden which the employer thus acquires. Section 10(c), as well as the Board's own regulation, make clear that the general counsel must prove the employer's guilt by a preponderance of the evidence to warrant a finding that an unfair labor practice has occurred. We think the only burden which may be acceptably placed on the employer is a "burden of production," that is a burden of coming forward with credible evidence to rebut or meet the general counsel's prima facie case. This, in effect, is the position we took recently in other cases although without actually characterizing the employer's burden as one of "production" rather than "persuasion." NLRB v. Amber Delivery Service, 651 F.2d 57 (1st Cir. 1981); NLRB v. Cable Vision, 660 F.2d 1 (1st Cir. 1981). We said in those cases that once the general counsel has established a basis for finding an improper motive, the employer must merely, "come forward with enough evidence to convince the trier of fact that, under the circumstances, there is no longer a preponderance of evidence establishing a violation." NLRB v. Amber Delivery Service, 651 F.2d at 69; NLRB v. Cable Vision, 660 F.2d at 8.

Professor Wigmore distinguishes between the burden of rebutting a prima facie case and the burden of persuading the trier of fact on the ultimate issue in a case by a preponderance of the evidence as follows:

"[A] 'prima facie' case ... need not be overcome by a preponderance of the evidence, or by evidence of greater weight; but the evidence needs only to be balanced, put in equipoise, by some evidence worthy of credence; and, if this be done, the burden of the evidence is met and the duty of producing further evidence shifts back to the party having the burden of proof ...."

9 Wigmore on Evidence § 2487, at 282 (3d ed. 1940), quoting Speas v. Merchants' Bank Trust Co., 188 N.C. 524, 125 S.E. 398 (1924).

Put another way, the general counsel's initial, prima facie showing creates a kind of presumption that an unfair labor practice has been committed. At this point, the employer risks losing his case unless he rebuts the presumption with evidence of his own. The Board may properly recognize this by stating that the employer (who alone has access both to the reason he discharged the employee and any corroborative evidence) now comes under a "burden" to produce evidence of a "good" reason for the discharge. The imposition of this limited burden, however, does not shift to the employer the burden of proving that an unfair labor practice has not occurred. Rule 301 of the Federal Rules of Evidence very aptly describes the scope of the duty involved in rebutting presumptions in civil cases as "the burden of going forward with evidence to rebut or meet the presumption," and distinguishes this duty from "the burden of proof in the sense of the risk of nonpersuasion, which remains throughout the trial upon the party on whom it was originally cast." Fed.R.Evid. 301. Thus, the employer in a section 8(a)(3) discharge case has no more than the limited duty of producing evidence to balance, not to outweigh, the evidence produced by the general counsel.

The Board may properly provide, therefore, that "Once [a prima facie showing] is established, the burden will shift to the employer to demonstrate that the same action would have taken place even in the absence of the protected conduct." 251 NLRB No. 150, at 20-21 (footnote omitted). The "burden" referred to, however, is a burden of going forward to meet a prima facie case, not a burden of persuasion on the ultimate issue of the existence of a violation.

We recognize that the Supreme Court's language in Mt. Healthy appeared to place an affirmative burden of persuasion on the employer. We further recognize that this court's acceptance of Mt. Healthy in some previous cases may have suggested that we, too, saw the burden upon the employer as, in all situations, a burden of persuasion. A closer look at Mt. Healthy, however, indicates a critical difference between that case and most labor cases. This difference does not affect the substantive utility of the "but for" analysis there employed, but does affect the nature of the employer's burden.

In Mt. Healthy, the employer conceded that he had fired the employee for speech activity which was later found to be fully protected under the first amendment. Thus, the "but for" test was not used, as it is in the typical labor case, as a part of the process of deciding whether a violation of protected rights had occurred. Rather, the "but for" test applied only after such a violation had been proven by the employer's own admission. The employer's claim, then, was a true affirmative defense to a rehiring order — i. e., the employer contended that notwithstanding his violation of the Constitution reinstatement was improper as a remedy because the employee had also been involved in an altercation with another teacher, an argument with cafeteria employees, and an incident in which he made obscene gestures to female students. The employer argued that these incidents, which were totally independent of the protected speech activity, justified the employee's dismissal notwithstanding the fact that the employer had violated the employee's constitutional rights. The employer's claim was thus a true affirmative defense which went to the appropriateness of the remedy being applied rather than to the existence of a violation in the first instance.

By contrast, in the typical labor case (and in the present case), the employer vigorously disputes the determining reason for the discharge. These cases therefore do not involve true affirmative defenses going to the appropriateness of the remedy, nor would the "but for" analysis be employed to determine the existence of such an affirmative defense. Rather, the "but for" test is in such cases a convenient formula for deciding whether or not an unfair labor practice has actually occurred — i. e., for deciding if the determining motive of the discharge was anti-union animus or some valid business reason. The "but for" standard requires a determination by the Board, based on all the evidence, that, wholly apart from an alleged illegal motive, the employer would (or would not) have discharged the employee for the conduct ascribed to him by the employer. If the discharge would have taken place irrespective of the anti-union motive, no unfair labor practice took place: if the discharge would not have taken place, it is clear that the determining reason for the discharge was the protected activity, not the reason given by the employer. With respect to this ultimate question of a determining causal link between the bad motive and the discharge, the burden of persuasion remains always with the general counsel. In the course of its inquiry, however, the Board and the ALJ are entitled to place a burden of production on the employer in the manner already described once a sufficient prima facie showing of illegal motive is made by the general counsel. Cf. Texas Department of Community Affairs v. Burdine, 450 U.S. 248, 101 S.Ct. 1089, 67 L.Ed.2d 207 (1981) (stating that burden of persuasion on the issue of discriminatory intent in Title VII cases remains always with the plaintiff).

It may be said by way of concluding our discussion on this point that labels concerning burdens of "persuasion" and "production" are not, as a practical matter, likely to be very important in most of these cases. Decision will usually turn on a weighing of all the evidence. But this weighing, under the Board's new formulation, will include a careful consideration of the employer's "good" reason as well as of the general counsel's evidence of improper motive. This approach will assure that due consideration is given to all facets of the case.

III.

Applying these principles to Wright Line's discharge of Bernard Lamoureux, we find substantial evidence to support a conclusion by the Board, on the preponderance of the evidence, that Lamoureux was discharged because of his union activity. We therefore affirm the Board's finding that Wright Line violated the Act in discharging Lamoureux, and that Lamoureux is entitled to reinstatement with back pay.

As background to the discharge, the general counsel presented evidence that Lamoureux was a leading union advocate and that Wright Line management was aware of Lamoureux's role. The evidence showed that management was aggressive in its opposition to the union and that management's hostility was on occasion directed at Lamoureux in particular. The general counsel also presented evidence of the circumstances surrounding the discharge itself. These circumstances, taken together and in the light of this background, support the Board's inference that the company was watching Lamoureux for any transgression that might provide an opportunity for discharge, and that it seized on Lamoureux's otherwise trivial offense to effectuate its true purpose of getting rid of an activist.

The evidence showed that Southard asked Forte to check on Lamoureux, who was entering the men's room with a newspaper, even though this conduct violated no company rule and even though Lamoureux had no history of laxity to warrant suspicion. Forte's "checking" consisted of measuring and documenting Lamoureux's absence; it did not include looking in the men's room or paging Lamoureux, even though Lamoureux's job was such that he might have been absent for a legitimate purpose. When Forte found Lamoureux after another absence later in the day, he did not ask for an explanation, although he apparently considered the absence significant enough to merit recording. From these facts, the Board could reasonably infer that Southard and Forte were primarily interested in building a case against Lamoureux rather than simply assuring that he attend properly to his work.

The events following Forte's review of Lamoureux's time report also support the inference of impropriety. Rather than confronting Lamoureux directly, as might be expected of a supervisor who discovers an apparent transgression by an otherwise satisfactory long term employee, Forte immediately consulted higher officials. These managers' first response was that the offense was "dischargeable"; they made the decision to discharge Lamoureux even before discussing the matter with him. By the time Lamoureux was called in, Forte had prepared his final paycheck and drafted a memorandum for the file. When Lamoureux finally received a chance to explain, his defense apparently fell on deaf ears. He conveyed no inability or unwillingness to make accurate time reports; rather his response suggested that he had not done so because he had not considered it important, and that he would do so if desired. Nevertheless, he was not warned or reprimanded, but discharged. From this and other evidence, mentioned hereinafter, the Board could reasonably infer that the inaccurate time report was seized upon to justify action taken for another reason.

This inference might have been overcome had there been evidence establishing that Wright Line would have fired employees in Lamoureux's position (whether or not union activists) for this sort of infraction. For example, it might have been proven that Wright Line was a consistently strict employer who commonly fired employees for rule violations no more serious than this, or else that this was in fact a violation very detrimental to its business which warranted discharge. Had this been done — had it been established that apart from union activity, Lamoureux would have been discharged for making such a time report — a finding for the employer would have been indicated. But no such conclusion was required on this record. Wright Line relies on its rule against "knowingly altering or falsifying production time reports." It emphasizes its use of Daily Activity Reports to verify performance of inspections, to evaluate individual inspectors, and to monitor staffing levels. But the Board concluded, with ample support in the record, that the time of each inspection, as opposed to the fact that each was done and the number done in a day, had no bearing on any of these calculations and received no notice from management. Lamoureux testified, and the Board was entitled to believe, that he had never been instructed to record times exactly, that he had never heard of any employee being criticized for inaccurate reporting of times, and that the general practice among inspectors was to record times in "round figures." The Board could conclude from the evidence that Lamoureux's offense affected no significant interest of his employer, and no interest that Wright Line had treated as significant.

Wright Line asserts that Lamoureux's "falsehood" proved him untrustworthy, and therefore unworthy of the reliance it must place on its inspectors. Clearly a showing of dishonesty would cause most employers to discharge an employee. The Board could reasonably doubt, however, that an employer would lose its trust in such a long term, satisfactory employee on the basis of an inaccuracy that cost the employer nothing and gained the employee nothing. Lamoureux's time report, under these circumstances, suggests no intention to falsify; at worst it demonstrates carelessness on a matter of little significance.

Further, the evidence showed that Wright Line's past practice in handling similar offenses had been quite different. The Administrative Law Judge found, based on testimony regarding the time required to perform inspections, that reports submitted by other inspectors contained "easily discernible" inaccuracies; yet no other inspector was ever disciplined in any way for inaccurate time reports. There was also evidence of an incident in which Wright Line's Chief Inspector had another employee punch her time card, a violation of the same rule. See note 15, supra. Even though such conduct strongly suggests deliberate falsification to cover an unexcused absence at the employer's expense, the Chief Inspector received only a warning; she was not discharged. There was evidence that Wright Line had discharged two employees for dishonesty, but both instances involved conduct amounting to outright theft from the company. One of these employees, an accountant, had embezzled funds, while the other, a salesman, had falsified his reports so as to collect unearned commissions. On this evidence, the Board was warranted in perceiving a difference between Wright Line's responses to Lamoureux's offense and its handling of comparable incidents of misconduct. The Board could reasonably infer from this that some other factor was involved in Lamoureux's case; and the background of Lamoureux's activism and the company's animus could be thought to supply the missing factor.

Further support for the Board's conclusion as to Wright Line's motivation comes from the ALJ's credibility judgments. To rebut the inference of improper motive, Wright Line presented the testimony of three of the officials involved in the discharge. Each related his own view of the incident, denying any concern for Lamoureux's "untrustworthiness," as shown by his false time report. The ALJ stated that, from the demeanor of the witnesses as well as from "the record as a whole . . . I do not believe that they were truthful in revealing the 'real reason' for Lamoureux's discharge." The ALJ's evaluation of Forte's testimony is particularly specific. He found that Forte appeared generally honest, until questioned about Lamoureux's discharge. "Here, being a generally truthful man, he showed physical signs of disassembling." The ALJ's credibility judgments must stand unless they are unreasonable, which these are not. Under these circumstances, the witnesses' untruthfulness strengthens the inference of unlawful motive. Shattuck Denn Mining Corp. v. NLRB, 362 F.2d 466, 470 (9th Cir. 1966).

On this record, the Board was justified in finding that the general counsel had proven, by a preponderance of the evidence, that Wright Line discharged Lamoureux because of his union activity in violation of section 8(a)(3) of the Act.

The petition for enforcement is granted.