If a Driver Seriously Injures or Kills Someone, Are They Automatically Tested for Drugs and Alcohol?

If a driver seriously injured or killed a cyclist, pedestrian, or another motorist, would police automatically test them for possible impairment?

Most Americans assume the answer is yes. After all, determining whether a driver was impaired seems like one of the first steps investigators would take after a fatal or life-changing crash.

Despite what many people believe, there is no federal law requiring drivers to automatically submit to drug or alcohol testing after causing a crash that results in serious injury or death. Instead, the decision to test often depends on state law, the circumstances of the crash, and whether law enforcement has reason to suspect impairment.

This issue gained national attention in 2026 after Colorado passed Magnus' Law, a new law requiring officers to offer a voluntary breath test to drivers involved in crashes resulting in death or suspected serious bodily injury. 

Why Aren't Drivers Automatically Tested for Impairment After a Serious Crash?

The answer largely comes down to constitutional protections.

In most cases, law enforcement cannot automatically require a driver to submit to a breath, blood, or drug test simply because the driver was involved in a serious crash. Depending on the circumstances, officers may need consent, probable cause, a warrant, or authority granted under state law.

Many states also have "implied consent" laws, which generally provide that drivers agree to chemical testing under certain circumstances as a condition of operating a motor vehicle. However, those laws vary significantly from state to state and do not always require testing after every serious injury or fatal crash.

As a result, whether a driver is tested after a crash often depends on the state where the crash occurred and the evidence investigators find at the scene.

How Do States Handle Serious Injury and Fatal Crashes?

There is no national standard for post-crash drug and alcohol testing. Some states give officers broader authority to request testing after fatal or serious injury crashes, while others rely primarily on traditional DUI investigations and probable cause.

One family in Colorado found themselves asking that very question after the death of 17-year-old cyclist Magnus White.

How One Family Changed Colorado's Crash Investigation Process

On July 29, 2023, 17-year-old cyclist Magnus White was training near his home in Boulder, Colorado. Riding on the shoulder of a designated bicycle route, Magnus was struck and killed by a driver.

Like many families, Michael and Jill White assumed law enforcement would investigate every possible factor that may have contributed to the crash, including whether the driver was impaired by drugs or alcohol.

They later learned that the driver was never offered an alcohol breath screening test.

What made the situation even more difficult was what emerged during the criminal proceedings. According to testimony presented at trial, the driver had allegedly stayed up all night drinking whiskey, using cocaine, and taking prescription medications that warned against driving. A friend reportedly urged the driver not to get behind the wheel that morning.

"The only person tested for drugs or alcohol that afternoon was Magnus," Michael White later wrote.

For the White family, the discovery was shocking. Like most Americans, they assumed impairment testing was a routine part of every fatal crash investigation. Instead, they spent nearly 20 months waiting for answers that could have begun with a simple question at the crash scene.

Their experience exposed a gap in Colorado's crash investigation process and ultimately sparked a bipartisan effort to change the law.

What Is Magnus' Law?

On June 4, 2026, Colorado Governor Jared Polis signed Senate Bill 26-132, better known as Magnus' Law.

The law requires law enforcement officers to offer a voluntary preliminary breath test to drivers involved in crashes resulting in death or suspected serious bodily injury. Drivers must be advised that they have the right to refuse the test.

Rather than creating a new crime or lowering DUI thresholds, Magnus' Law establishes a consistent statewide investigative protocol. Officers must offer the test and document whether the driver consented, refused, or the test could not be administered due to equipment issues or other circumstances beyond the officer's control.

Supporters argue the law is not about presuming guilt. It is about ensuring investigators ask an important question while the evidence is still available.

As Michael White explained during the bill signing ceremony:

"Evidence at a crash scene is the most fragile thing in the world. It exists for a moment, and then it is gone. If you do not capture the truth at the scene, you may never capture it at all."

The bill received overwhelming bipartisan support before being signed into law.

Why Is the Test Voluntary?

One of the most common questions about Magnus' Law is why lawmakers chose to make the breath test voluntary rather than mandatory.

The answer largely comes down to constitutional protections and Colorado law. Magnus' Law was designed to ensure officers consistently offer the test and document the outcome. Drivers may consent or refuse, but the question can no longer be overlooked.

Why Aren't Drug Tests Offered Like Breathalyzers?