Missouri’s 2026 DWI law changes, explained

Change 1: every injury and death tier moves up a felony class

This is the headline. Under the old ladder, criminal negligence causing physical injury was a class E felony. As of August 28 it is a class D felony. Serious physical injury moves from class D to class C. Causing a death moves from class C to class B or higher.

The old statute also broke out separate categories for particular victims — law enforcement and emergency personnel, non-passengers, deaths of two or more people, deaths where BAC was .18 or higher. Those are deleted and folded into the general provisions.

One drafting point we will flag rather than paper over: the amended statute classifies causing a death as a class B felony in one subdivision and a class A felony in another, and the two overlap. The legislature attached different parole minimums to each — five years and ten years — which suggests both were intended to operate. Until courts sort it out, no one can tell you with certainty which applies. Be skeptical of any site that states one flatly.

Change 2: ignition interlock became mandatory on first-offense privileges

Under the old rule, a first-offense administrative suspension gave you a choice: serve 30 days with no driving followed by 60 days of restricted driving, or install an ignition interlock and get 90 days of restricted driving immediately with no hard suspension.

The amended statute changes a single word — the notice must now indicate that an interlock is required, rather than whether one is required. In practice, interlock becomes mandatory on first-offense restricted driving privileges rather than the price of avoiding a hard suspension.

It does not make an interlock mandatory on every first offense. The requirement attaches to the restricted privilege, and nothing compels you to apply for one. A first offender under .15, with no property damage or injury, who serves the 30-day hard suspension and does not drive for the following 60 days can reinstate without a device. The trade is three months of not driving. Separately, the criminal court can still order an interlock on a first offense under RSMo 302.440, so the administrative track is not the whole picture.

The mandatory-interlock triggers also expand, and no prior offense is needed to hit them. From August 28, if your driving record shows a conviction for an intoxication-related traffic offense in which your BAC was .15 or higher, or in which you caused any property damage or personal injury, an interlock becomes a required condition of restricted driving privileges and of reinstatement (RSMo 302.304.17(2), 302.525.2(3) and .5, and 302.574.10), and the court must order one under RSMo 302.440. Note what that turns on: a conviction or a finding of guilt, not an arrest. A .15 breath result on a case that is still pending, gets dismissed, or is amended to a non-intoxication offense produces no qualifying entry on your record.

There is one provision running the other way, and it is worth knowing about: interlock providers must adopt a discounted fee schedule for people with income at or below 150% of the federal poverty level, who then pay 10% of the device cost.

Change 3: Bentley and Mason’s Law

HB 1740 creates an entirely new obligation at RSMo 454.1050. It applies once a person is convicted of, pleads guilty to, or pleads no contest to DWI or BWI under RSMo 577.010 or 577.012 and that offense caused the death of a child’s parent. The surviving parent or guardian must then petition — nothing happens automatically — and on that petition the court shall order the offender to pay child maintenance. Payments run until the child turns 18, extendable to 21 where the child is enrolled in secondary school or higher education, and longer for a physically or mentally incapacitated child.

The statute coordinates this with civil recovery rather than stacking on top of it. If the surviving parent obtains a civil judgment before a maintenance order, no maintenance is ordered. If maintenance is ordered first, it offsets any later civil judgment, and any payment from a motor vehicle liability insurer offsets the maintenance order. The amount is whatever is reasonable or necessary for the child’s maintenance, set after the court weighs all relevant factors. The statute lists six of them — the child’s needs and resources, the surviving parent’s or guardian’s resources and needs, the standard of living the child would have had, the child’s physical and emotional condition and educational needs, the custody arrangement, and reasonable work-related child care — but the list is expressly open, and the court must also apply Missouri’s child support guidelines and Form 14.

What has not changed

• The definition of the offense itself — operating a vehicle while in an intoxicated condition — is untouched
• First offense is still a class B misdemeanor; prior offender is still a class A misdemeanor
• The .08 threshold and the separate excessive-BAC statute are unchanged
• The 15-day deadline to request a Department of Revenue hearing is unchanged
• The 30-day suspension plus 60-day restricted period durations are unchanged
• Refusal still carries a one-year revocation