What is the test for dismissing a prior felony?

In deciding whether to dismiss a prior felony for purposes of applying the three strikes law, a court "'must consider whether, in light of the nature and circumstances of his present felonies and prior serious and/or violent felony convictions, and the particulars of his background, character, and prospects, the defendant may be deemed outside the scheme's spirit, in whole or in part, and hence should be treated as though he had not previously been convicted of one or more serious and/or violent felonies.' [Citation.]" (People v. Carmony (2004) 33 Cal.4th 367, 377.) "The striking of a prior serious felony conviction is not a routine matter. It is an extraordinary exercise of discretion, and is very much like setting aside a judgment of conviction after trial." (People v. Jackson (1986) 178 Cal.App.3d 694, 697-698.)

We review an order denying a motion to dismiss a prior strike for abuse of discretion. (People v. Carmony, supra, 33 Cal.4th at p. 375.) "[A] trial court does not abuse its discretion unless its decision is so irrational or arbitrary that no reasonable person could agree with it." (Id. at p. 377.) "'[I]t is not enough to show that reasonable people might disagree about whether to strike one or more' prior conviction allegations. [Citation.] Where the record is silent [citation], or '[w]here the record demonstrates that the trial court balanced the relevant facts and reached an impartial decision in conformity with the spirit of the law, we shall affirm the trial court's ruling, even if we might have ruled differently in the first instance' [citation]." (Id. at p. 378.)