## Facts

- Sandra Carlson drove through a stop sign and blinking red light at an intersection in Spencer, Massachusetts, and struck the passenger side of another vehicle.
- The passenger, Carol Suprenant, had severe chronic obstructive pulmonary disease and used supplemental oxygen; she had expressed that she did not want to be kept alive on a ventilator.
- The collision caused Suprenant multiple chest wall fractures (ribs and sternum) and a lung contusion.
- Suprenant was hospitalized, intubated, and placed on a ventilator.
- Suprenant requested discontinuation of the ventilator and was removed from intensive care; she later agreed to re-intubation as breathing worsened.
- When her kidneys began to fail, Suprenant again chose to discontinue the ventilator and decline dialysis after being advised death was likely without them and that continued treatment offered a reasonable chance of survival.
- Suprenant died several hours after the ventilator was removed, from respiratory failure.
- A treating physician testified that, but for the crash injuries, Suprenant likely would not have needed a ventilator and would not have faced the decision whether to accept life-sustaining treatment.

## Issues

1. Whether Carlson’s negligent operation of a motor vehicle was a proximate cause of Suprenant’s death when Suprenant later refused life-sustaining treatment that likely would have prolonged her life.
2. Whether the trial court’s intervening/superseding-cause instructions were inadequate, creating a substantial risk of a miscarriage of justice.

## Decision

- The Supreme Judicial Court affirmed Carlson’s conviction for motor-vehicle homicide by negligent operation.
- The court held the evidence permitted a finding beyond a reasonable doubt that Carlson’s negligence was a proximate cause of death.
- The victim’s refusal of life support was not, as a matter of law, a superseding cause that relieved Carlson of criminal liability.
- The jury instructions, considered as a whole, adequately conveyed causation and intervening-cause concepts; any arguable imprecision did not create a substantial risk of a miscarriage of justice.

## Legal Principles

- A defendant is a legal cause of death when her conduct, in a natural and continuous sequence, produces death and death would not have occurred without it.
- An intervening event breaks the causal chain only if it is a superseding cause that is independent of the defendant’s conduct and sufficiently extraordinary and unforeseeable to relieve criminal liability.
- A defendant takes the victim as found; preexisting vulnerabilities do not bar liability when the defendant’s conduct sets in motion the chain leading to death.
- A competent victim’s decision to refuse or discontinue medical treatment, including life-sustaining treatment, ordinarily is a foreseeable consequence of the condition created by the defendant and does not itself sever proximate causation.

## Conclusion

The court concluded that negligent driving that caused injuries leading to ventilator dependence could be found a proximate cause of death even when the competent victim later refused life-sustaining care, because that decision did not constitute an independent, extraordinary superseding cause.


Commonwealth v. Carlson, 447 Mass. 79 (2006)