What is the test for a defendant to be treated as if he had not previously been convicted of serious and/or violent felonies?

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." (People v. Williams (1998) 17 Cal.4th 148, 161.)

Two fundamental precepts guide our appellate review. First, the appealing party bears the burden " ' "to clearly show that the sentencing decision was irrational or arbitrary. [Citation.] In the absence of such a showing, the trial court is presumed to have acted to achieve legitimate sentencing objectives, and its discretionary determination to impose a particular sentence will not be set aside on review." ' [Citation.]" (People v. Carmony, supra, 33 Cal.4th at pp. 376-377.) "Second, a ' "decision will not be reversed merely because reasonable people might disagree. 'An appellate tribunal is neither authorized nor warranted in substituting its judgment for the judgment of the trial judge.' " ' [Citation.] Taken together, these precepts establish that 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.)