dissenting.
T 44 To the majority, an unexplained injury that occurs at work is equivalent to being attacked by car thieves, struck by lightning, or hit by a stray bullet. Maj. op. 128-24. I disagree. The cause of such "neutral risks" in those cases is perfectly clear-that is, the car thieves, the lightning bolt, or the stray bullets. Such injuries are covered by workers compensation because work put the claimant in the position to be injured by the causal foree-that is, the thief, bolt, or bullet. Here, by contrast, the ALJ determined that the cause of Rodriguez's injury was unexplained, and therefore found the injury (correctly in my view) non-compensable. To put it differently, Rodriguez failed to prove that her injury "arose out of" her employment. By deeming such unexplained injuries com-pensable, the majority significantly expands the scope of workers' compensation coverage in Colorado. Because such decisions are, in my view, better left to the legislature, I respectfully dissent.
45 As the majority notes, before Rodriguez may recover for her injury under Colorado's Workers' Compensation Act, she must establish by a "preponderance of the evidence" that the injury occurred "in the course of" and "arising out of" her employment. - Maj. op. 116, citing §§ 8-4l-301(1)(c), 8-48-201(1), C.R.S. (2018). The "arising out of" test requires a claimant to prove "a causal connection between the work conditions and the injury." In re Question Submitted by the U.S. Court of Appeals for the Tenth Ciremit, T59 P.2d 17, 22 (Colo. 1988); see also Heinicke v. Indus. Claim Appeals Office, 197 P.3d 220, 223 (Colo.App. 2008) (noting that a right to workers' compensation benefits does not arise "[where causation cannot be established").
1 46 In this case, as the majority observes, the ALJ did eliminate some potential causes of Rodriguez's injuries, finding that neither the condition of the stairs nor her preexisting brain aneurysms caused the fall. Maj. op. 119, 20, 22. But eliminating these two potential causes only shows two factors which did not cause the fall, and none that did. Without sufficient evidence to determine why Rodriguez fell, the ALJ ultimately concluded that the ecause of the fall was "unexplained." Maj. op. 19. Because the cause of the fall was unexplained, Rodriguez could not, and did not, establish causation, and thus she did not carry her burden to show by a preponderance of the evidence that her injuries arose out of employment. In my view, we should simply affirm the ALJ's determination in all respects.
147 The majority nevertheless breathes new life into Rodriguez's claim by placing her *510unexplained fall on equal footing with "neutral risks" like car thieves, lightning bolts, or stray bullets. Maj. op. 123-24. These risks are not merely neutral, however; they are also known. If an injury were to arise from any of these causes, the claimant could demonstrate to the ALJ not only how she was injured, but more importantly, that the injury "would not have occurred but for the fact that the conditions and obligations of employment placed the employee in the position" where she was exposed to the risk of being injured. Maj. op. 12; see also In re Question, 759 P.2d at 22-25 (finding that an assault victim's injuries arose out of employment because work obligations caused her to be present at the time and place where she was exposed to the "neutral" threat of the random assault); Aetna Life Ins. Co. v. Indus. Comm'n, 81 Colo. 288, 285-36, 254 P. 995, 996 (1927) (affirming an award of compensation for an employee whose employment obligations required him to be at the particular place where he was struck by lightning).
{48 The majority's error, however, is to expand the concept of "neutral risks" to include injuries that occur at work where the cause is mot known. Such an unexplained injury is not categorically "neutral," as the majority would have it Rather, an unexplained injury defies categorization. It could have been caused by a neutral risk, but it could also be the result of an entirely personal risk of harm, or of an occupational hazard. In other words, "but for" the claimant's presence at work, the injury could have occurred anyway. Unlike an injury resulting from a known, neutral threat, an unexplained fall by definition does not establish causation, and therefore cannot satisfy the claimant's obligation to demonstrate that an injury arose out of employment.
T49 Significantly, the majority does not question the ALJ's conclusion that the cause of Rodriguez's injury could not be determined, or offer a cause of its own. Yet somehow, the majority finds it "clear" that "Rodriguez's fall was not the result of an occupational hazard, nor a personal risk." Maj. op. 124. In doing so, the majority extends the ALJ's ruling well beyond its purview. - Far from ruling out all occupational hazards or personal risks as potential causes of the injury, the ALJ held only that the fall was not precipitated by Rodriguez's brain aneurysms, or by her tripping or missing a step or by any dangerous condition on the stairs. Id., 19. After eliminating these potential causes-and only these potential causes-the ALJ then concluded that the fall was "unexplained." Id. Rather than extrapolating from this modest holding the broad conclusion that no occupational hazard or personal risk could have caused the injury, the majority should take the ALJ's determination for what it is: a testament to Rodriguez's failure to establish that her injuries arose out of her employment.
1 50 Compounding this error, the majority next implies that the ALJ required Rodriguez to prove the "precise mechanism" of her fall, and thus applied too strict of a causal test. Maj. op. 1% 18, 24. That simply is not the case. The ALJ applied the well-established "preponderance of the evidence" standard. By finding that the cause of the fall was unexplained, however, the ALJ correctly determined that Rodriguez could not meet the burden of proof required to establishing the cause of her injury. Thus, the ALJ's determination was not the result of Rodriguez being required to bear an excessive burden. The burden which the ALJ placed upon Rodriguez was correct; she simply failed to carry that burden.1
1 51 More significantly, the majority's position extends the ability position to receive worker's compensation well beyond the seope prescribed by statute. The majority denies that its holding suggests "that all injuries that occur at work are compensated under workers' compensation law." Maj. op. 129. But by placing unexplained injuries on equal *511ground with injuries with neutral (and known) causes, the majority makes it possible to receive compensation after merely demonstrating that an injury was sustained on the job. This has never been enough, at least until today, to establish entitlement to workers' compensation-a causal connection must be shown. See § 8-41-301(1)(c); see also In re Question, 759 P.2d at 22. Otherwise, it would have been unnecessary for the legislature to have included the "arising out of" requirement. See Fetzer v. N.D. Workforce Safety and Ins., 815 N.W.2d 589, 548-44 (N.D.2012) (holding, in a case involving an unexplained fall, that the "but-for reasoning of the positional risk doctrine is inconsistent with our statute that requires claimants to prove a causal connection between their employment and injury"). Thus, by holding that unexplained injuries are compensable, the majority significantly expands the scope of workers' compensation coverage in Colorado. Because I believe this expansion is an issue best left to the legislature, I respectfully dissent from the majority's opinion.
I am authorized to state that Justice COATS joins in this dissent.
. - The majority also holds that the City, seeking to modify an issue previously determined by an admission, failed to meet its burden of proving by a preponderance of the evidence that such a modification should be made. Maj. op. 11 39-41. As the majority observes, however, this holding rests on the conclusion that unexplained falls can be compensable under the "but-for" test." Id., 141. As shown above, this premise is incorrect. I would hold instead that where the ALJ concluded that the cause of the fall was unexplained, the City met its burden.