Causation in California DUI Injury and DUI Manslaughter Cases
When a California DUI case involves a serious accident, injury, or death, it can be tempting to assume that the driver's intoxication automatically makes the driver criminally responsible for the resulting harm. California law requires more.
In prosecutions for DUI causing injury under Vehicle Code section 23153 and vehicular manslaughter while intoxicated under Penal Code section 191.5, causation is a separate and important element of the prosecution's case.
A driver can be under the influence and involved in an accident without necessarily being the legal cause of another person's injury or death. For a Northern California DUI defense attorney, examining how and why the collision occurred can therefore be just as important as challenging the prosecution's evidence of intoxication.
DUI Causing Injury Requires More Than Driving Under the Influence
California Vehicle Code section 23153 applies when a person drives under the influence and, while doing so, commits an unlawful act or neglects a legal duty in driving that proximately causes bodily injury to another person.
The California jury instructions similarly require the prosecution to prove that the defendant's illegal act or failure to perform a legal duty caused bodily injury to another person.
This distinction matters.
Suppose a driver has a blood-alcohol concentration above the legal limit but is proceeding lawfully through an intersection on a green light. Another vehicle runs a red light and crashes into the driver's vehicle, injuring its passenger.
The mere fact that the first driver was legally intoxicated does not necessarily establish that the driver's conduct caused the collision or injury.
The prosecution must prove the causal connection required by section 23153.
People v. Capetillo and Causation in DUI Injury Cases
One particularly useful California decision concerning this issue is People v. Capetillo (1990) 220 Cal.App.3d 211.
The Court of Appeal explained that a section 23153 prosecution requires proof that:
The defendant drove while under the influence;
While driving, the defendant violated the law or failed to perform a legal duty; and
As a proximate result of that violation or failure, another person was injured.
Importantly, the unlawful act or neglect of duty is a requirement separate from intoxicated driving itself.
In Capetillo, the prosecution could not simply rely upon the fact that the defendant's unlawful conduct placed his vehicle at the location where the collision occurred. The Court of Appeal distinguished that type of "but for" reasoning from the proximate causation required for DUI causing injury. The evidence did not establish what or who actually caused the collision, and the court ultimately reduced the felony DUI conviction to the lesser DUI offense.
That distinction can provide an important starting point for the defense of an injury DUI case.
"But For" Causation Is Not Necessarily Enough
There is an important difference between saying:
"The accident would not have occurred if the defendant had not been driving."
and saying:
"The defendant's unlawful driving conduct proximately caused the accident and resulting injury."
The first proposition may establish nothing more than the defendant's presence at the scene.
As Capetillo demonstrates, simply showing that the defendant's conduct was part of the chain of events leading to an accident does not necessarily establish the required proximate cause.
For the defense, this means the investigation should not end with BAC evidence. The fundamental question may instead be: What actually caused the collision?
What If the Other Driver Caused the Accident?
This can become particularly important when there is evidence that another driver contributed to the collision.
For example, evidence might show that another motorist:
Ran a red light or stop sign;
Made an unsafe lane change;
Entered the roadway unexpectedly;
Was speeding;
Failed to yield;
Was distracted by a phone;
Drove on the wrong side of the road; or
Otherwise created the circumstances producing the collision.
The prosecution may have strong evidence that the defendant consumed alcohol and still face a genuine causation problem.
Indeed, Capetillo noted that the prosecution's evidence did not exclude negligence by the other driver as the cause of the accident.
That is why accident reconstruction evidence can become extremely important in a DUI causing injury prosecution.
Causation in DUI Manslaughter Cases
Causation becomes even more consequential when an accident results in death.
California Penal Code section 191.5 addresses vehicular manslaughter while intoxicated. Subdivision (a), involving gross negligence, requires an unlawful killing resulting proximately from the specified negligent conduct while the defendant is driving in violation of California's DUI laws. Subdivision (b) addresses vehicular manslaughter while intoxicated without gross negligence.
Once again, intoxication and death occurring in the same accident do not eliminate the prosecution's obligation to prove causation.
The prosecution must connect the defendant's legally culpable driving conduct to the death.
Gross Vehicular Manslaughter While Intoxicated
Penal Code section 191.5(a) addresses gross vehicular manslaughter while intoxicated.
Among other requirements, the statute requires the killing to be the proximate result of an unlawful act not amounting to a felony committed with gross negligence, or a lawful act that might produce death performed in an unlawful manner and with gross negligence.
Consequently, several issues can exist independently in a manslaughter case:
Was the defendant intoxicated?
Was the defendant negligent or grossly negligent?
Did that conduct actually and proximately cause the victim's death?
The prosecution must establish the elements required by the particular offense. Evidence supporting one issue does not automatically establish the others.
Injury Versus Death
The relationship between DUI causing injury and DUI manslaughter illustrates why causation matters.
California courts have explained that a person who causes an injury while driving under the influence may violate Vehicle Code section 23153, and if the victim dies from that injury, Penal Code section 191.5 may apply. People v. Miranda (1994) 21 Cal.App.4th 1464 addressed that relationship, and the Court of Appeal recently discussed it again in People v. Meno (2024).
The critical connection is that the injury or death must result from the conduct satisfying the statutory causation requirements.
Intervening Causes in DUI Cases
Another important issue is whether something occurred after the defendant's conduct that affected the causal chain.
Depending on the particular facts, potential causation questions can involve:
Another driver's actions. A second driver's unexpected or dangerous maneuver may be relevant to determining what actually caused the collision.
Road conditions. Construction, debris, standing water, defective roadway design, missing signs, or malfunctioning traffic signals may require investigation.
Mechanical failure. Brake failure, tire failure, steering problems, or another mechanical defect may affect accident reconstruction and causation.
The conduct of a pedestrian or bicyclist. Their actions immediately before the collision may be important to reconstructing what happened.
Events after the collision. Particularly in homicide cases, the defense may need to examine whether subsequent events affect the causal relationship between the collision and death.
The existence of another contributing factor does not automatically eliminate criminal causation. But it can make a detailed reconstruction of the accident essential.
Accident Reconstruction Can Be Critical
When a DUI involves catastrophic injury or death, the defense should independently investigate the collision rather than simply accept the conclusions in the police traffic-collision report.
Important evidence can include:
Event data recorder or "black box" information;
Vehicle speed and braking data;
Airbag control module information;
Skid and tire marks;
Vehicle damage;
Surveillance and dash-camera footage;
Traffic-light timing data;
Cellphone evidence;
Roadway measurements;
Photographs and drone imagery;
Witness statements; and
Accident reconstruction analysis.
This evidence can answer questions that a chemical test cannot.
A BAC result may provide evidence concerning intoxication. It does not, by itself, explain why two vehicles collided.
A High BAC Does Not Answer the Causation Question
This distinction is particularly important in cases involving a high BAC.
The prosecution may emphasize a chemical result because it is powerful evidence that the defendant should not have been driving. But the emotional significance of a high BAC should not substitute for proof concerning how the accident happened.
Consider a defendant stopped at a red light who is struck from behind by another vehicle. Evidence that the stopped driver had a .15 percent BAC may be highly relevant to a DUI charge. But the BAC itself does not establish that the driver's intoxication caused the collision.
In a DUI causing injury or DUI manslaughter prosecution, the defense should separate these questions rather than allowing them to become conflated.
Defending a DUI Causing Injury or DUI Manslaughter Case in Northern California
Cases involving serious injury or death require careful investigation because the consequences can be substantial.
A Northern California DUI defense attorney handling a case in Chico, Butte County, Glenn County, Tehama County, Yuba County, Sutter County, or surrounding areas should evaluate both sides of the prosecution's case: the evidence of intoxication and the evidence establishing how the collision actually occurred.
Causation can sometimes become overshadowed by a high BAC, serious injuries, or a tragic death. But those circumstances do not eliminate the prosecution's burden of proving the statutory elements of the charged offense.
The defense question should remain straightforward:
What conduct actually caused the injury or death, and can the prosecution prove that conduct was attributable to the defendant beyond a reasonable doubt?
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