Can they reduce it to an infraction? Yes. Do they have to reduce it? No.
In the state of California (and all other states whose laws I am aware of) any theft of a thing of even slight value is presumed to be a misdemeanor unless it is so valuable as to make it a "grand" theft whereupon it becomes a felony.
If they reduce the charge against you from a misdemeanor to an infraction it will probably be because they don't want to do the trial, and you have no previous record. Under those cirucmstances you might even convince the court to sentence you to DEJ (Deffered Entry of Judgment, sometimes called "Deffered Action") whereby you would never actually be convicted of anything as long as you stayed out of trouble for 18 months.
Same question over and over again = same answer over and over again. See one of the tens of answers previously, mine included.
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