What is the test for determining whether a defendant has a history of serious and/or violent felonies under the Three Strikes scheme?

the People . . . ." ' " (Romero, supra, 13 Cal.4th at p. 530, italics omitted.) The trial court must accord "preponderant weight . . . to factors intrinsic to the [Three Strikes] scheme, such as the nature and circumstances of the defendant's present felonies and prior serious and/or violent felony convictions, and the particulars of his [or her] background, character, and prospects." (People v. Williams (1998) 17 Cal.4th 148, 161.) "[N]o weight whatsoever may be given to factors extrinsic to the scheme, such as the mere desire to ease court congestion or, a fortiori, bare antipathy to the consequences for any given defendant. [Citation.]" (Ibid.) Ultimately, the trial court must determine whether "the defendant may be deemed outside the scheme's spirit, in whole or in part, and hence should be treated as though he [or she] had not previously been convicted of one or more serious and/or violent felonies." (Ibid.)