What is the burden of presenting a peremptory challenge?

"A party who suspects improper use of peremptory challenges must raise a timely objection and make a prima facie showing that one or more jurors has been excluded on the basis of group or racial identity. The high court has explained that the defendant is required to `raise an inference' that the exclusion was based on group or race bias. [Citation.] Once a prima facie showing has been made, the prosecutor then must carry the burden of showing that he or she had genuine nondiscriminatory reasons for the challenges at issue." (People v. Jenkins (2000) 22 Cal.4th 900, 993, 95 Cal.Rptr.2d 377, 997 P.2d 1044 (Jenkins)).