Texas requires an ignition interlock device in more DWI situations than most drivers realize. In some cases, the device is ordered at bond hearings, in plea deals, and as a condition of getting your license back. For some drivers, they’re required by statute. For others, they’re negotiable.
Dallas judges often may order interlocks as a condition of bond before any conviction. That means you’re paying for a device on a case you haven’t lost yet—and the time you spend on it pre-trial doesn’t always count toward your post-conviction requirement.
RJ Harber is a Dallas DWI defense attorney and former prosecutor with over 15 years of experience handling these cases. If you’re facing a DWI charge or an interlock requirement, contact us today for a free consultation.
How Texas Ignition Interlock Devices Work
An ignition interlock device is a breath-test mechanism wired into a car or truck’s ignition. Before the engine starts, the driver must blow into the device. If the unit detects alcohol above a preset limit, the engine stays locked. The device also prompts rolling breath samples at random intervals while driving.
After installation, vendors run monthly calibration checks, and every event gets logged: start attempts, BAC readings, failed tests, and missed retests. The reports are sent to the court or supervising agency. The driver pays for the installation and the monthly monitoring fee.
Ignition Interlock as a Texas DWI Bond Condition
Texas Code of Criminal Procedure article 17.441 requires an ignition interlock as a bond condition in certain DWI cases, with the judge deciding at the bond hearing before any conviction.
The rule is mandatory for a second or subsequent conviction under Penal Code section 49.04 (DWI), on the first offense for DWI with a child passenger (49.045), intoxication assault (49.07), or intoxication manslaughter (49.08).
Once the device is ordered, the defendant has 30 days from the date of release to install it. The defendant pays for installation and the monthly fee to the supervising agency, which the statute caps at $10 per month.
For a first DWI without those aggravators, the order is discretionary. Whether the device gets ordered usually turns on the defendant’s record and how the case is being charged.
Ignition Interlock as a Texas DWI Probation Condition
DWI With A 0.15 BAC Or Higher
Article 42A.408(c)(1) makes ignition interlock mandatory on community supervision when the trial showed blood, breath, or urine analysis with an alcohol concentration of 0.15 or more at the time of testing.
The court has no discretion under this provision. The device is ordered for at least 50 percent of the supervision period, with installation due within 30 days of conviction.
Prior DWI Convictions Within 10 Years
Article 42A.408(c)(3) requires interlock on community supervision when the court determines the defendant has at least one prior conviction under Penal Code sections 49.04 through 49.08, which covers DWI and related intoxication offenses.
Under subsection (d), the court pulls the defendant’s record from the Department of Public Safety to determine whether there are prior counts.
A prior conviction is excluded only if:
- It was committed before the 10-year window preceding the current offense, and also
- The defendant has had no other 49.04-49.08 conviction within that 10-year window.
Otherwise, the prior counts and interlock are required.
Drivers Under 21 at the Time of the Offense
Subsection (e) of article 42A.408 imposes an interlock automatically when the defendant was under 21 at the time of the offense and is placed on community supervision after a conviction under Penal Code sections 49.04 through 49.08.
The age cutoff applies to the date of the offense, not the date of conviction. The provision applies even when other subsections might otherwise allow flexibility.
Deferred Adjudication for DWI
Article 42A.408(e-1) requires interlock as a condition of deferred adjudication community supervision for offenses under Penal Code section 49.04 (DWI).
The court may waive the requirement under subsection (e-2) only after a controlled substance and alcohol evaluation, and only if the court enters a finding on the record that an interlock is not necessary for community safety.
For an indigent defendant, subsection (e-1) lets the court reduce the costs by waiving the installation charge and cutting the monthly device monitoring fee in half.
Ignition Interlock for an Occupational Driver’s License
After a DWI conviction, the driver’s regular license is typically suspended. A driver may apply for an occupational license to drive for work, school, and essential household duties under Texas Transportation Code.
Texas Transportation Code section 521.246 governs when an ignition interlock device is required as a condition of that occupational license. The interlock stays installed for the duration of the suspension period unless the court finds both good cause to remove it and that the device is not necessary for community safety.
There is a narrow employer-vehicle exemption: If the driver must operate a vehicle in the course of employment, the vehicle is owned by the employer, and the employer is not controlled by the driver, the law allows the driver to use that work vehicle without an interlock so long as proof of the employer’s notice is kept in the vehicle.
Contact a Dallas DWI Defense Lawyer
If you’ve been ordered to install an ignition interlock, or you’re facing a DWI charge that may bring one, the timing of your defense matters. The Law Offices of RJ Harber have 15+ years of experience with DWI cases involving ignition interlocks. Contact us today for a free consultation.
Frequently Asked Questions
Who is required to install an IID after a Texas DWI conviction?
Texas law often requires an ignition interlock device installed in the vehicle of a driver convicted of DWI, particularly in cases involving a second DWI conviction or a high BAC reading. For a first DWI offense, the judge may still order the device based on the circumstances. When the BAC device detects 0.15 or higher and the driver is placed on community supervision, an interlock is mandatory under the Texas Code of Criminal Procedure.
For how long must the IID stay installed?
In Texas, the device must typically remain installed for the period set by the court, generally ranging from six months to up to two years, depending on the offense and the driver’s history. For a second or subsequent DWI committed within five years of the prior offense, Texas Penal Code section 49.09(h) requires the interlock to remain installed until one year after the license suspension period ends. The court sets the exact length based on the conviction and any conditions attached to the sentence.