There has been a recent increase in DUI cases involving drivers under the influence of nitrous oxide — commonly referred to as "whippets" — including three fatality cases in San Diego County over the past year, authorities said Thursday.

While nitrous oxide is legal for a variety of purposes ranging from medical to culinary, California has criminalized the recreational use of the drug, which involves inhaling the gas. Statewide, possession of nitrous oxide for recreational purposes or being under the influence of the drug for recreational purposes is a misdemeanor offense.

But prosecutors say charging nitrous oxide-related DUI cases presents unique challenges, as toxicology tests might not detect the drug because it leaves the user's system so quickly.

Since October of last year, the Sa

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