McBride v. Superior Court
In McBride v. Superior Court, 130 Ariz. 193, 194, 635 P.2d 178, 179 (1981), the petitioners obtained a personal injury judgment in January 1979 with a statutory interest rate of 6 percent. 130 Ariz. at 193, 635 P.2d at 178.
The petitioners argued that a December 1979 amendment to A.R.S. 44-1201(A), which increased the rate of interest on a judgment from 6 percent to 10 percent per annum, applied to their judgment. Id. at 193-94, 635 P.3d at 178-79.
The Supreme Court agreed, holding that "interest on a judgment is a statutory and not a contractual obligation, and when the interest rate is changed by statute, the rate of interest on a judgment is also changed." Id. at 194, 635 P.2d at 179.
Thus, the Court found that the petitioners were entitled to 6 percent interest from the date of the judgment until the effective date of the amendment, and 10 percent interest thereafter. Id.