CA SB421

Establishes misdemeanor diversion program for first-time DUI offenders with no prior DUI convictions and who have not completed diversion in the past 10 years, limited to non-commercial drivers and subject to prosecution approval.

Requires diversion participants to install ignition interlock devices (IID) for at least 12 months and complete education/counseling programs (minimum 30 hours for low BAC, 60 hours for 0.2% BAC or higher or refusal).

Mandates ignition interlock device installation for first-time DUI convictions with a mandatory 6-month minimum term; eliminates option for restricted license without IID for first offenders.

Requires IID manufacturers to maintain participant files for three years including installation, service, calibration, and removal records, with department access to all records.

Counts DUI charges dismissed through diversion as prior convictions for purposes of subsequent DUI offenses and requires the Department of Motor Vehicles to track diverted arrests in DUI data.

Extends IID installation period by 60 days if driver attempts vehicle start with alcohol detected during final 60 days of mandatory term; provides credit toward mandatory term for voluntary pre-conviction IID installation.