How has a defendant been convicted of possession of cocaine base for personal use?

Defendant admitted that he had been convicted of three drug offenses in 1990, that he had been twice convicted of possession for sale of marijuana in the 1980's, and that he had been convicted of robbery in 1981. The parties stipulated that defendant had five convictions of drug offenses, and they tended to negate possession of the cocaine base for personal use. The prior conviction of robbery, a crime of moral turpitude, was relevant to defendant's credibility. (See People v. Collins (1986) 42 Cal.3d 378, 395.)

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