What is the effect of mind-altering substances on the inference of a person's subjective mental state from their conduct in a second-degree murder case?

The inference of an individual's subjective mental state from his conduct generally proceeds on the assumption that the individual is cognitively intact and would comprehend what a reasonable (i.e. cognitively intact) person would comprehend under the circumstances. This predicate assumption is disrupted by evidence that a defendant's cognitive functioning is impaired by mind-altering substances. Under California law, therefore, voluntary intoxication that prevents subjective appreciation of risk precludes a finding of malice and reduces second-degree murder to manslaughter. People v. Saille, 54 Cal. 3d 1103, 1116-17 (1991); People v. Whitfield, 7 Cal. 4^th 437, 451 (1994). Petitioner's evidence creates a reasonable doubt as to appreciation of risk.