In People v. Tenner (1993) 6 Cal.4th 559, the California Supreme Court summarized the requirements for a prior prison term enhancement: "Imposition of a sentence enhancement under Penal Code section 667.5 requires proof that the defendant: (1) was previously convicted of a felony; (2) was imprisoned as a result of that conviction; (3) completed that term of imprisonment; (4) did not remain free for five years of both prison custody and the commission of a new offense resulting in a felony conviction." (Id. at p. 563.) "Due process requires the prosecution to shoulder the burden of proving each element of a sentence enhancement beyond a reasonable doubt." (Id. at p. 566.) To prove the element that a defendant "completed his term of imprisonment," an "abstract of judgment and commitment form can suffice as proof," although the "better practice" is to introduce into evidence a "prison packet" under section 969b (certified records or copies of records of a prison or jail). (Id. at p. 567.)