It does not matter if the individual is convicted of a DUI - Even if they are found "not-guilty" or is never prosecuted for a DUI, the interlock device will be required.
All first time DUI offenders and those individuals who refuse to take a roadside test for alcohol or drugs will be required to install an interlock device on any vehicle they plan to drive. An interlock device requires the operator to blow into the system before the vehicle will function; if the device finds alcohol in the driver's system the vehicle will not function. Previously, individual judges had the discretion to decide if an interlock device was necessary on a case-by-case basis. For the most part, this meant that interlock devices were only required for repeat offenders.