Pursuant to provisions of the Westfall Act, see 28 U.S.C. § 2679, the United States moved to substitute itself as the sole defendant in a defamation suit brought by Aníbal Taboas against nine federal employees. The *578 district court'denied the motion for substitution, holding that the defendant employees were not acting within the scope of their employment when they made the allegedly defamatory statements. We reverse the district court’s decision and remand for further proceedings.
I.
Aníbal Taboas was a manager in the Department of Energy’s field office in Argonne, Illinois from 1987 to 1995. Eight employees in the Argonne office filed individual and class discrimination grievances against Ta-boas in 1995, alleging that Taboas had favored minority candidates in hiring and promotion decisions and had favored female candidates with whom he had a personal or sexual relationship. Shortly after filing their grievances, the employees became dissatisfied with the handling of their case. Their case counselor reportedly informed them that Cherri Langenfeld, Taboas’s supervisor, refused to take action against Taboas for fear of provoking a lawsuit.
The employees then sent a letter to the ease counselor’s supervisor, a DOE official based in Golden, Colorado, to complain about the lack of response to their concerns. This letter also conveyed the employees’ fears that Taboas would retaliate against them, perhaps violently, because of their grievances. The letter described several alleged incidents of erratic behavior by Taboas, including faking a suicide at a party attended by DOE employees; carrying an M-16 assault rifle, which he had fraudulently obtained from the Argonne armory, around the office; and displaying a large hunting knife while at work. The Colorado supervisor referred the matter back to Langenfeld in the Chicago Operations Office, who declined to act on the employees’ concerns because of a lack of supporting evidence. The employees initiated a separate grievance against Lan-genfeld, and they also brought the matter to the attention of then-Secretary Hazel O’Leary of the Department of Energy and two Illinois congressmen.
The, DOE commissioned a contractor to evaluate the likelihood that Taboas would engage in violent reprisals. The contractor, a forensic psychologist, concluded that the employees’ concerns were baseless. According to his report, the employees had relied on unsubstantiated hearsay and not first-hand knowledge, and much of their information had been fed to them by a disgruntled security employee, Edward McCallum, who had worked in the Argonne facility with Taboas before being transferred to Washington, DC.
Taboas sued the eight employees from the Argonne office, as well as Edward McCallum, in Illinois state court. The complaint alleged defamation, tortious interference with his employment relationship, and other state-law claims. Pursuant to the Westfall Act, the United States certified that the nine defendants were acting within the scope of their employment and moved to substitute itself as the sole defendant. 1 The parties consented to the referral of the case to a magistrate judge, who denied the motion to substitute on the grounds that the defendants were not acting within the scope of their employment. According to the magistrate judge, the defendants acted solely in *579 their own interests, as demonstrated by then-attempt to circumvent the established chain of command in bringing their complaints before Secretary O’Leary and the two congressmen. The United States appeals from the denial of the motion. 2
II.
Taboas contends that we lack jurisdiction over this appeal because the denial of the motion for substitution is not a final order.
3
We have taken jurisdiction of such an appeal in the past, however,
see Snodgrass v. Jones,
Furthermore, since substitution effectively confers immunity, the same limitations on appealability that apply to a denial of qualified or absolute immunity also apply to a denial of a motion for substitution.
Johnson v. Jones,
In this case, the magistrate judge did not identify or rely on disputed issues of fact in denying the motion for substitution.
*580
Rather, the order relied on the “unrebut-ted exhibit evidence presented by plaintiff’ in concluding that, as a matter of law, “the plaintiff has met his burden of showing that the defendants’ conduct was outside the scope of employment.” The magistrate judge reached this conclusion based on the fact that the defendants had made their complaints, contrary to the established policy of the Department, outside of the proper chain of command. Taboas argues that there is a genuine factual dispute regarding the defendants’ states of mind in making the alleged defamatory statements, • and he contends that this disputed factual issue prevents us from taking jurisdiction over this appeal. The magistrate judge’s order made no finding regarding malice, however, and it did not rely on the defendants’ subjective states of mind in denying the substitution motion. Johnson does not authorize an appellee to defeat appellate jurisdiction under the collateral order doctrine by asserting the existence of factual disputes that are never identified, or relied upon, by the district court in denying the defendant’s claim of immunity as a matter of law.
See Johnson,
The parties also dispute the appropriate standard of review on appeal. In
Snod-grass,
we stated that the district court’s determination that the defendant acted outside the scope of his employment was subject to
de novo
review.
Snodgrass v. Jones,
As: noted, substitution of the United States as .the exclusive defendant under the Westfall. Act confers immunity on the defendant employee. In requesting immunity through substitution, the movant 4 has the same procedural options as a defendant asserting other forms of immunity, such as an absolute or qualified immunity defense. An immunity defense is typically asserted in one of two ways. Immunity may be raised in a motion to dismiss, in which case the district court accepts as true all factual allegations in the complaint and decides whether immunity attaches as a matter of law. Alternatively, an immunity defense may be raised in a motion for summary judgment, in which case the district court ascertains whether any genuine issue of material fact exists and, if there is none, decides whether judgment is warranted as a matter of law.
These same avenues are available in requests for immunity under the Westfall Act. A motion for substitution may be decided on the face of the complaint (akin to a motion to dismiss) when the movant contends that, even accepting the allegations of the complaint as true, the defendant acted within the scope of employment.
See McHugh v. University of Vermont,
The more difficult question is how to proceed when the motion for substitution contests the facts pled in the complaint, as in a motion for summary judgment, and the summary judgment papers reveal disputed factual issues. In such a case, the district court may hold an evidentiary hearing to resolve material factual disputes related to the scope of employment.
5
Resolution of factual disputes in preliminary seope-of-employment proceedings is a significant departure from typical summary judgment practice, in which “a trial court’s function is to ascertain whether disputed facts exist, not to try them.”
Melo,
In the instant case, the debate surrounding evidentiary hearings under the Westfall Act is not an issue, for the magistrate judge proceeded along the traditional summary judgment model and was not required to resolve any factual disputes. The magistrate judge noted the parties’ agreement “that the motion could be decided on the papers filed,” and he went on to make an independent determination “that the motion is, in fact, decidable on those papers.” The magistrate *582 judge looked to “the motion and memorandums filed with respect to the motion, ... the exhibits attached to plaintiffs opposition memorandum ... [and] plaintiffs first amended verified complaint (and exhibits),” and the court based its decision to deny the motion on “the unrebutted exhibit evidence presented by plaintiff.” The magistrate judge conducted a typical summary judgment proceeding, and, as in any summary judgment case, our standard of review is de novo.
III.
With these preliminary issues now resolved, we turn to the merits of the district court’s denial of the motion for substitution. Whether the defendants’ action fell within the scope of employment is decided under state law,
see Snodgrass,
Under Illinois law, “[n]o precise definition has been accorded the term ‘scope of employment,’ but broad criteria have been enunciated.”
Pyne v. Witmer,
Bringing a supervisor’s perceived misfeasance to the attention of his superiors is among the duties that an employee may reasonably be expected to perform.
See Bue-chele v. St. Mary’s Hosp. Decatur,
Moreover, the accusations against Taboas at least in part promoted the employer’s interest in a safe workplace. Taboas maintains that the allegations were made with malice and in bad faith, which, he contends, cannot promote any legitimate interest of the employer. Although the suggestion has been made that malice, bad faith, or self-interested motivation necessarily places conduct outside the scope of employment,
see Ramsey,
Taboas points to the consultant’s report as evidence that the employees’ fears of violent reprisal were baseless, but the report sheds Httle light on the defendants’ subjective motivations other than to note the defendants’ tendency to rely on unsubstantiated hearsay. Taboas’s allegations of malice are also contradicted by Cherri Langenfeld’s contemporaneous impression, as described in an exhibit to Taboas’s complaint, that the defendants “honestly feel that their expressed concerns are real.” Thus, Taboas fails to meet his burden of demonstrating that the defendants’ complaints were entirely unmotivated by a desire to alert superiors to a potentially dangerous workplace situation. We conclude, therefore, that the defendants acted within the scope of employment.
IV.
Because the individual defendants were acting within the scope of their employment, we reverse the denial of the United States’ motion for substitution as the sole defendant in this ease, and we remand for further proceedings.
Notes
. The Westfall Act, officially known as the Federal Employees Liability Reform and Tort Compensation Act of 1988, Pub.L. No. 100-694, 102 Stat. 4563 (1988), amended several provisions of the Federal Tort Claims Act to extend immunity to federal employees from liability for tortious conduct occurring within the scope of employment. When a tort action is brought against a federal employee, the Attorney General may certify that the employee "was acting within the scope of his office or employment at the time of the incident out of which the claim arose.” 28 U.S.C. § 2679(d)(1). This "scope certification” by the Attorney'General serves to substitute the United States as the sole defendant,
id.
§ 2679(d)(1), and, if the suit was filed in state court, the case is removed to federal court,
id.
§ 2679(d)(2). Since the action against the United States is the plaintiffs exclusive remedy,
id.
§ 2679(b)(1), substitution of the United States as the sole defendant serves to immunize the defendant employee from liability.
See, e.g., Ezekiel v. Michel,
. Prior to filing this appeal, the United States moved the district court to reconsider its denial of substitution. The magistrate judge denied this motion with respect to eight of the defendants but granted the motion with respect to Defendant McCallum. Thus, the proceedings regarding Defendant McCallum are not involved in this appeal.
. Taboas also argues that we lack jurisdiction because the individual defendants filed their notices of appeal more than 30 days after the denial of the motion for substitution. The 30-day period for filing an appeal did not begin to run, however, until the district court rejected the United Státes' timely motion to reconsider the denial of substitution, see Fed. R.App. P. 4(a)(4), and the notices of appeal were filed within 30 days of that decision.
. When the Attorney General certifies that the employee acted within the scope of employment, the United States moves for substitution. See 28 U.S.C. § 2679(d)(1). When the Attorney General declines to certify, the defendant employee may petition the court for a scope certification and substitution of the United States as the defendant. See id. § 2679(d)(3).
. We note that when the district court resolves factual disputes relating to scope of employment in an evidentiary hearing, the restrictions on immediate appealability imposed by
Johnson v. Jones,
. The one significant exception is a phone call from one of the defendants to Taboas's ex-wife. According to Taboas, this phone call sought to dredge up any information or "dirt” that his ex-wife could provide in support of the defendants’ allegations. This one incident, however, does not place the defendants' overall course of conduct outside the scope of their employment. The test is whether the conduct occurs "substantially within the authorized time and space limits,” and the record shows that the bulk of the negative statements about Taboas were made on the job to responsible officials with colorable authority over the parties involved.
