CYR, Senior Circuit Judge.

Plaintiffs appeal from a district court judgement dismissing their equal protection claims against the Town of Lisbon, New Hampshire, and its chief of police, Richard Grayson, for failing to investigate allegations that their father abused them sexually while they were minors. We affirm.

I. [2] BACKGROUND

Although the three sisters first lodged these allegations in 1983, Grayson took no action other than to misrepresent that the district attorney had declined to prosecute. Seven years later, after attaining their majority, plaintiffs discovered Grayson's misrepresentation and took their allegations to the district attorney. Their father presently is serving a lengthy prison sentence, following his conviction for aggravated sexual assault.

Plaintiffs filed the instant action against the Town and Grayson, in his individual and official capacities, claiming inter alia that Grayson refrained from investigating their allegations either because plaintiffs were female, children, or victims of domestic sexual abuse, and that such selective law enforcement violated their individual rights under the Equal Protection Clause. See U.S. Const. amend XIV; 42 U.S.C. § 1983. In due course, the equal protection count against the Town was dismissed for failure to state a claim. See Fed.R.Civ.P. 12(b)(6). Following discovery, defendant Grayson was awarded summary judgment on the individual-capacity claim because plaintiffs had failed to adduce sufficient evidence that he intended to discriminate due to their membership in any of the three classes alleged in their complaint. The district court thereafter denied plaintiffs' post-judgment motion for reconsideration. See Fed.R.Civ.P. 59.

II. [5] DISCUSSION [6] A. The Equal Protection Claim Against Grayson

The Fourteenth Amendment mandates that no State "deny to any person within its jurisdiction the equal protection of the laws." U.S. Const. amend XIV. Thus, although there is no constitutional right to police protection, State executive and law enforcement officials may not "selectively deny . . . protective services to certain disfavored minorities.: DeShaney v. Winnebago County Dep't of Social Servs., 489 U.S. 189, 197 n. 3 (1989).

Plaintiffs rely on City of Cleburne v. Cleburne Living Ctr., 473 U.S. 432 (1985), for their contention that the district court should not have applied the equal protection test governing race and gender classifications, which necessitated that plaintiffs show that Grayson acted with discriminatory intent. Instead, plaintiffs argue, in cases involving less invidious but nonetheless arbitrary classifications, such as child victims of domestic sexual abuse, Cleburne simply envisions that plaintiffs prove that the defendant's decision lacked a "rational basis," without regard to any discriminatory intent.

Plaintiffs misconstrue the Cleburne decision. There the Supreme Court expressly noted the finding made by the district court that the municipality's principal reason for denying the requested zoning permit had been "that the residents of the [plaintiff] home would be persons who are mentally retarded," id. at 437, a finding which was never challenged on appeal. Thus, it was only because the city's discriminatory motive had been established ab initio that the Court addressed whether the city need demonstrate a "compelling" or "important" state interest — criteria theretofore reserved for race and gender discrimination — or need simply articulate a "rational basis" for its decision. Id. at 440-41. Accordingly, Cleburne did not hold that no threshold proof of intent to discriminate is required in cases involving less invidious arbitrary classifications.

The motivation underlying a municipal decision is not always so apparent as in Cleburne, of course, especially if the challenged decision does not expressly single out a particular class of persons for disadvantageous treatment. Even in such instances, however, members of the plaintiff class quite understandably may consider it no mere coincidence that a facially neutral decision causes a disproportionately unfavorable impact on their particular class. Nevertheless, even evidence of a widely disproportionate impact on the plaintiff class normally is not enough, standing alone, to establish an equal protection violation. See, e.g., Personnel Adm'r of Mass. v. Feeney, 442 U.S. 256, 274-75 (1979) (upholding veteran's preference in civil service hiring, although vast majority of veterans hired were male). Rather, plaintiffs must adduce competent evidence of "purposeful discrimination." Washington v. Davis, 426 U.S. 229, 243-44 (1976); Soto v. Flores, 103 F.3d 1056, 1067 (1st Cir.), cert. denied, 118 S.Ct. 71 (1997).

The burden is an onerous one: "'Discriminatory purpose' . . . implies that the decisionmaker . . . selected or reaffirmed a course of action at least in part 'because of,' not merely 'in spite of,' its adverse effects upon an identifiable group." Feeney, 442 U.S. at 279 (emphasis added; citation omitted); Soto, 103 F.3d at 1067. Thus, unless these plaintiffs established the requisite discriminatory intent, their equal protection claim cannot succeed even assuming the Grayson decision not to investigate lacked a "rational basis." See Village of Arlington Heights v. Metropolitan Hous. Dev. Corp., 429 U.S. 252, 265 (1977); Semple v. City of Moundsville, 963 F. Supp. 1416, 1433 (N.D. W. Va. 1997).

Plaintiffs claim that the district court disregarded competent evidence that Grayson harbored "archaic stereotypes" regarding female-child sexual abuse in the home and singled out its victims for unfavorable treatment in determining whether to investigate. The record does not support their contention, however.

At no time did Grayson indicate to anyone that he would not investigate allegations of child sexual abuse in the home because he thought the victims were undeserving of equal law-enforcement protection. Instead, he explained to a fellow officer that he had refrained from investigating plaintiffs' allegations at their mother's request. Another police officer confirmed that it was Grayson's policy not to intervene where a family member (e.g., nonabusive parent or spouse) requested that there be no investigation.

Plaintiffs essentially claim, nonetheless, that their evidence supported, respectively, rational inferences that Grayson intended to treat all domestic crime differently from nondomestic crime, all crimes against children differently from crimes against adults, and all sexual abuse crimes differently from non-sexual crimes. Once again the evidence does not bear out their claim.

Plaintiffs' proffer disclosed that the nonintervention policy attributed to Grayson may have been much broader than plaintiffs allow, in that it applied not merely to domestic child sexual abuse, but to other crimes in circumstances where general concerns for family integrity and family privacy predominated. Thus, their proffer may be seen to belie their contention that Grayson sought to discriminate against them because of, rather than in spite of, their status as victims of child sexual abuse in the home. See Feeney, 422 U.S. at 279. Far from demonstrating general condonation of child sexual abuse in the home, therefore, the proffer simply supported a reasonable inference that Grayson would investigate virtually any allegation of crime absent an appropriate request from a nonoffending spouse to refrain from intervention in circumstances where legitimate, competing family interests were thought to predominate. Accordingly, although the evidence may well have demonstrated that the Grayson nonintervention policy had a disproportionate adverse impact in cases involving allegations relating to the various victim classes in which plaintiffs claimed membership, it did not demonstrate that Grayson harbored a discriminatory animus toward those victim classes. Id. at 274 (upholding veteran's preference in civil service hiring, even though vast majority of veteran hirees were male).

Similarly, plaintiffs presented evidence that Grayson, on two other occasions, failed to investigate allegations of child sexual abuse in the home. Once again, however, there was no evidence that Grayson was motivated by a discriminatory animus, as distinguished from a neutral nonintervention policy. Moreover, Grayson proffered undisputed evidence that he had investigated at least two other domestic child sexual abuse cases, as well as eight nondomestic child sexual abuse cases. Cf. Willhauck v. Halpin, 953 F.2d 689, 712 (1st Cir. 1991) (in analogous context of equal protection claim founded on selective prosecution, "[i]t must be shown that others similarly situated have not been prosecuted and that the decision to prosecute has been motivated by an impermissible reason").

Finally, in an ironic twist, the discriminatory focus essential to plaintiffs' equal protection claims was irredeemably blurred by their proffer that the Grayson nonintervention policy extended well beyond domestic child sexual abuse cases (e.g., to DWI and vandalism), and may even have been due to Grayson's dishonesty, chronic lassitude, alcohol abuse, or desire to wage personal vendettas against particular individuals rather than groups. See New Burnham Prairie Homes, Inc. v. Village of Burnham, 910 F.2d 1474, 1481 (7th Cir. 1990) (noting that "[d]iscrimination based merely on individual, rather than group, reasons will not suffice" to establish equal protection violation). That is to say, although their scattershot approach might enable a rational inference that Grayson was a poor police chief, it cannot sustain a nonspeculative inference that he failed to investigate these allegations because plaintiffs were children who had been sexually abused, or because plaintiffs had been sexually abused in the home. See Soto, 103 F.3d at 1072 ("Whether this deplorable scenario is actionable under Puerto Rican law we leave, as we must, to others.").

B. The Equal Protection Claim Against the Municipality

The district court dismissed the equal protection count against the Town for failure to state a claim. See Fed.R.Civ.P. 12(b)(6). Eighteen months later, plaintiffs moved to reinstate and amend the claim, see Fed.R.Civ.P. 15, to allege that the Town should be held liable either because Grayson was the municipal official who instituted the official "policy" against providing law-enforcement protection to child victims of sexual abuse in the home, see Monell v. Department of Social Servs. of New York, 436 U.S. 658, 694-95 (1978), or because the Town failed to train Grayson adequately to deal with domestic child sexual abuse, which constituted "much" or "most" of the crime in the community.

The district court denied the motion to amend, on the ground that its earlier Rule 12(b)(6) dismissal amounted to a decision "on the merits" and, accordingly, the law of the case. Even assuming the rationale for the instant decision were to be found infirm, see Griggs v. Hinds Junior College, 563 F.2d 179, 180 (5th Cir. 1977) (noting that Rule 15 amendment is "especially appropriate . . . when the trial court has dismissed the complaint for failure to state a claim"); see also Dussouy v. Gulf Coast Inv. Corp., 660 F.2d 594, 598 n. 2 (5th Cir. 1981), we would affirm on the ground that the proposed amendment would have been futile. See Levy v. FDIC, 7 F.3d 1054, 1056 (1st Cir. 1993).

Rule 15 permits the trial court to deny leave to file an amended complaint which would be subject to immediate dismissal under Rule 12(b)(6) for failure to state a viable claim for relief. See Foman v. Davis, 371 U.S. 178, 182 (1962); Mills v. State of Me., 118 F.3d 37, 55 (1st Cir. 1997). The Town cannot be held vicariously liable in an action under section 1983 unless its official policy or custom was the "moving force" behind the alleged violation of constitutional rights. See Monell, 436 U.S. at 694. Normally, therefore, a municipality cannot be held liable unless its agent actually violated the victim's constitutional rights. See City of Los Angeles v. Heller, 475 U.S. 796, 799 (1986) ("If a person has suffered no constitutional injury at the hands of [any] individual police officer, the fact that the departmental regulations might have authorized [unconstitutional action] is quite beside the point.").

Plaintiffs simply allege that the Town is liable under section 1983 because Grayson established an official Town policy or custom of selective law enforcement which in turn caused them injury. Since their predicate claim against Grayson fails, however, see supra Section II.A, so must their contention that any such discriminatory Town policy or custom existed.

Alternatively, of course, the Town could be held liable under section 1983 were it to appear that the injury to plaintiffs was caused by the Town's failure to train Grayson. The liability criteria for "failure to train" claims are exceptionally stringent, however. See City of Canton v. Harris, 489 U.S. 378, 388-89, 391 (1989).

Only if the failure to train "amounts to deliberate indifference to the rights of persons with whom the police come into contact," and is "closely related" to, or "the moving force" behind, the constitutional injury, can the claim against the municipality prevail. Id. (emphasis added). For this "deliberate or conscious choice" to have been established, plaintiffs needed to present evidence that (1) the Town knew when it hired Grayson that the risk of future equal protection violations arising and recurring in domestic child sexual abuse cases was "so obvious" that its failure to train him therein likely would result in continued violations; or (2) even though the initial risk of recurring constitutional violations was not "so obvious," the Town subsequently learned of a serious recurrence, yet took no action to provide the necessary training. Id. at 390 n. 10; see also id. at 396 (O'Connor, J., concurring in part).

To begin with, plaintiffs merely allege that "Lisbon is a high crime area in northern Grafton County [and] that much or most of the crime committed in northern Grafton County involves domestic violence and sexual abuse." (Emphasis added.) There is no allegation that these circumstances obtained in 1975, however, when Grayson became the police chief. No less importantly, even assuming similar circumstances prevailed in 1975, the need to train Grayson was not "so obvious, [nor] the [alleged] inadequacy [of the training] so likely to result in the violation of constitutional rights, that the [Town] can reasonably be said to have been deliberately indifferent to the need [for training]." City of Canton, 489 U.S. at 390.

It bears reminding that the gravamen of the amended complaint is not that Grayson did not adequately investigate these allegations, but that he purposely chose not to investigate them at all. It is reasonable to observe, therefore, that whatever relevant training the Town failed to give Grayson would not have entailed specialized law-enforcement investigatory skills, but simply the commonplace understanding that police officers may not deny law-enforcement protection based simply on their arbitrary classifications of various groups of crime victims.

Thus, the amended complaint asserted no sufficient basis for concluding that Town policymakers reasonably should have anticipated that a new police chief would need specialized instruction in so rudimentary a law-enforcement responsibility, nor that the Town had been put on notice that such equal-protection violations were routine occurrences in domestic child sexual abuse cases, either locally or elsewhere. Rather, unlike many other law-enforcement responsibilities, cf., e.g., id. at 390 n. 10 (noting that it might be considered "obvious" that armed police officers assigned to arrest fleeing felons would need instruction regarding constitutional limitations on proper use of deadly force), the Equal Protection Clause bar against arbitrary law enforcement is neither obscure nor problematic of application.

Finally, plaintiffs have not alleged that the Town was ever placed on notice that Grayson, after he was appointed in 1975, routinely violated the equal protection rights of citizens by engaging in selective and arbitrary law enforcement. See Swain v. Spinney, 117 F.3d 1, 11 (1st Cir. 1997) (lack of notice of prior constitutional violations defeats failure-to-train claim). Accordingly, we conclude that the proposed amendment to the complaint would have been futile.

Needless to say, our conclusion represents no endorsement of the conduct with which Grayson is charged in the complaint. It would be dereliction of duty for a police chief to turn over to private parties the decision whether a serious offense should be pursued and it is hard to imagine what might justify telling a complainant falsely that the prosecutor would have no interest in the complaint. Nevertheless, not every form of misconduct is a constitutional violation — most wrongs find their remedy under state law — and our present holding is simply that the allegations made in the complaint do not properly assert a violation of the Equal Protection Clause.

Affirmed.