SUMMARY ORDER

Dutchess County Sheriffs Deputy Benjamin Sistarenik appeals from an interlocutory order of the United States District Court for the Southern District of New York (Stein, J.) denying his motion for summary judgment on the basis of qualified immunity. We assume the parties’ familiarity with the underlying facts, the procedural history, and the issues presented for review.

Typically, “[t]he denial of a motion for summary judgment is ... not immediately appealable because such a decision is not a final judgment.” Jones v. Parmley, 465 F.3d 46, 54 (2d Cir. 2006) (internal quotation marks omitted). The collateral-order doctrine, however, provides a limited exception, under which “the denial of a qualified-immunity-based motion for summary judgment is immediately appealable to the extent that the district court has denied the motion as a matter of law, although not to the extent that the defense turns solely on the resolution of questions of fact.” Id. (internal quotation marks omitted). In other words, this Court has appellate jurisdiction “to determine whether a [a disputed factual] issue is material, but not whether it is genuine.” Bolmer v. Oliveira, 594 F.3d 134, 141 (2d Cir. 2010).

1. As to the excessive force claim, we dismiss for lack of appellate jurisdiction.

Relying on conflicting witness testimony, the district court held that “a reasonable jury could conclude that Healy was no longer resisting the officers when he was tased,” Dist. Ct. Op. at 15; that “Healy did not pose an immediate threat to the safety of the officer[s] or others at the time Sis-tarenik tased Healy,” Dist. Ct. Op. at 17; and that “Sistarenik ... administered] two taser shocks against Healy in short succession without advance warning and while Healy was restrained on the floor by four other officers,” Dist. Ct. Op. at 21.

It cannot be disputed that the fact issue of whether (and to what extent) Healy presented a threat at the time Sistarenik used the taser is material. See, e.g., Amnesty Am. v. Town of W. Hartford, 361 F.3d 113, 124 (2d Cir. 2004) (“Because a reasonable jury could ... find that the officers gratuitously inflicted pain in a manner that was not a reasonable response to the circumstances, ... the determination as to the objective reasonableness of the force used must be made by a jury following a trial.”). On appeal, Sistar-enik refuses to accept plaintiffs version of the facts, and argues — just as he did in the district court — that “[f]rom Sistarenik’s perspective[, Healy] presented a live and continuing threat,” Appellant’s Br. at 21, at the time of the tasing. Perhaps he did; perhaps he did not. But we lack appellate jurisdiction to review the genuineness of these factual disputes. Bolmer, 594 F.3d at 141.

2. As to the due process claim for denial of medical care, we affirm the denial of summary judgment. Sistarenik’s only argument on appeal is that, although the four state troopers on the scene had a duty to provide medical care to Healy, Sistare-nik had no such duty because he was a “non-custodial officer.” Appellant’s Br. at *63 29. Sistarenik cites no authority for this proposition.

In any event, the argument is forfeited, because Sistarenik raised it for the first time in his reply brief in support of his motion for summary judgment. Presumably, that is why the district court did not address the argument (in what is otherwise a thorough written opinion). Accordingly, we decline to consider it for the first time on appeal. See, e.g., Dalberth v. Xerox Corp., 766 F.3d 172, 184 (2d Cir. 2014).

For the foregoing reasons, and finding no merit in Sistarenik’s other arguments, we hereby AFFIRM the order of the district court, in part; and DISMISS for lack of appellate jurisdiction, in part. '