The court found that the Model Penal Code required a subjective analysis of whether provocation is adequate from the defendant's perspective.
Traditionally, the provocation had to be external to the defendant, but §210.3(I)(b) of the Model Penal Code moved away from this by defining manslaughter as a homicide that is "committed under the influence of extreme emotional or mental disturbance for which there is reasonable explanation or excuse".
In the Dumlao case the court interpreted this language broadly to permit consideration of reasonableness from the defendant's viewpoint when evaluating whether the provocation was adequate.
This allowed the jury to take the defendant's "mental abnormalities" into account, instead of adhering to the traditional objective reasonable person standard.
The Court concludes that Dumlao had a psychological disorder which may have caused an extreme emotional disturbance during which, from his viewpoint, his actions were reasonable.