In DeSchaaf v. Indus. Comm'n of Ariz., 141 Ariz. 318, 320, 686 P.2d 1288, 1290 (App. 1984), the ICA denied compensation to a claimant who had suffered an on-the-job stroke that she attributed to work-related stress. DeSchaaf, 141 Ariz. at 319, 686 P.2d at 1289. The ALJ ruled that the claimant had failed to meet her burden under A.R.S. 23-1043.01(A) (1995), which provided, in relevant part, that "a heart-related or perivascular injury, illness or death shall not be considered a personal injury by accident arising out of and in the course of employment and is not compensable . . . unless some injury, stress or exertion related to the employment was a substantial contributing cause of the . . . injury, illness or death." DeSchaaf, 141 Ariz. at 320, 686 P.2d at 1290. In her special action petition to this court, the DeSchaaf claimant argued that the "substantial contribution" requirement of 23-1043.01(A) conflicted with the principle in Article 18, Section 8, of the Arizona Constitution that injuries are compensable if caused "in part, or are contributed to" by necessary employment risks or dangers. Id. The court disagreed, explaining that although the legislature cannot alter legal causation as set forth in Article 18, Section 8, the "substantial contribution" requirement of 23-1043.01(A) pertained only to medical causation - whether the industrial accident caused the injury. Id. at 321, 686 P.2d at 1291. Legal causation in that case concerned whether the necessary risks or dangers of the claimant's employment caused her industrial accident (extreme stress). Medical causation concerned whether the stress caused her injury (the stroke). Because the "substantial contribution" requirement pertained only to the quantum of proof necessary to show that the industrial accident caused the injury, the court held that 23-1043.01(A) did not conflict with Article 18, Section 8. Id.