## Facts

- Cynthia Steinhauser, age 14, rode with her parents in a southbound car in Essex County, New York.
- A northbound car owned by The Hertz Corporation and driven by Louis J. Ponzini crossed a double yellow line into the southbound lane and struck the Steinhausers’ car on the left side.
- The occupants suffered no bodily injuries.
- Within minutes, Cynthia’s parents observed marked behavioral changes, including agitation and hostility; over the following days she reported paranoid fears, assaulted her parents, became depressed, and attempted suicide.
- Cynthia was hospitalized and ultimately diagnosed with an acute undifferentiated schizophrenic reaction; her treating psychiatrist later described a chronic schizophrenic reaction with a poor prognosis and likely need for continued care.
- Evidence suggested some pre-accident emotional difficulties and a prior minor concussion from a fall, but no pre-accident symptoms comparable in severity to those after the collision.
- Plaintiffs’ psychiatric evidence supported that Cynthia had a predisposition and that the collision precipitated the psychotic break; defendants argued she was already schizophrenic before the accident.

## Issues

1. Whether the trial court erred by framing causation as an all-or-nothing choice—either the accident caused Cynthia’s schizophrenia or she was already schizophrenic—without permitting the jury to find that the accident precipitated or accelerated a latent condition.
2. Whether the jury instructions and handling of expert proof deprived plaintiffs of a fair opportunity to have the jury consider the “precipitation/activation” theory of causation.

## Decision

- The Second Circuit reversed the defense judgment and remanded for a new trial.
- The court held the jury charge improperly confined causation to sole, direct causation and did not allow the legally available finding that the accident triggered or aggravated a latent schizophrenic condition.
- Because the charge prevented the jury from evaluating plaintiffs’ supported theory that the collision precipitated the illness, the error required a new trial.

## Legal Principles

- A negligent defendant is liable for harm when the defendant’s conduct precipitates, activates, or accelerates a dormant or latent disease or susceptibility into symptomatic illness, even if the plaintiff was predisposed.
- Causation in such cases does not require proof that the defendant’s act was the exclusive cause; it is enough that the act was a substantial factor in bringing about the harmful manifestation or worsening.
- Jury instructions must permit jurors to consider and apply a precipitation/aggravation theory when supported by evidence, rather than forcing a binary choice between preexisting disease and defendant-created disease.

## Conclusion

The appellate court ordered a new trial because the jury was not properly instructed that defendants could be liable if their negligence precipitated or accelerated Cynthia’s latent predisposition to schizophrenia, even if some vulnerability existed before the collision.


Steinhauser v. Hertz Corp., 421 F.2d 1169 (2d Cir. 1970)