According to Wikipedia, an Ignition Interlock Device is:
a mechanism, like a breathalyzer, installed on a motor vehicle’s dashboard. Before the vehicle’s motor can be started, the driver first must exhale into the device; if the resultant breath-alcohol concentration analyzed result is greater than the programmed blood alcohol concentration, the device prevents the engine from being started.
Once the vehicle has started, the device is going to randomly require additional samples to prevent someone other than the driver from blowing into the machine. If the driver fails to provide a sample, or the sample shows an impermissible alcohol concentration, the machine will log the event and then set off an alarm until the vehicle is turned off or a clean breath sample is provided.
Under Montana law, an IID can be required because of different situations. The newly created sentencing statute for Aggravated DUI specifically contemplates use of the machine as a part of a suspended sentence. But don’t think that these are only limited to aggravated charges.
Under Section 61-8-442, an IID may be required on a conviction for DUI
or DUI per se. In the case of a person’s first conviction it is left to the Court’s discretion to decide whether or not to require the interlock device. In my experience, it is rarely required for first time offenders not charged with Aggravated DUI. However, because extreme situations exist this is left to the judge’s discretion. However, when facing a second or subsequent conviction for DUI, the court must either require the IID for any period of a probationary license, require the person to participate in the 24/7 program, or order that each vehicle owned by the person be seized and forfeited.
Interlock devices are inconvenient, but better than not being allowed to drive. For most of my clients, the more pressing concern is the cost and the invasive nature of the device.