What is relevant evidence in a motor vehicle accident trial?

Relevant evidence is evidence "having any tendency in reason to prove or disprove any disputed fact that is of consequence to the determination of the action." (Evid. Code, 210.) Additionally, an expert witness may give opinions "[r]elated to a subject that is sufficiently beyond common experience" to assist the trier of fact. (Evid. Code, 801, subd. (a).) It is not unusual for medical experts to testify regarding the substantiality of alleged great bodily injuries. (People v. Clay (1984) 153 Cal.App.3d 433, 459 ["Medical doctors obviously have greater knowledge than lay jurors about the

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gravity of most injuries . . . ."].) Furthermore, the seriousness of a victim's injuries may constitute circumstantial evidence of a defendant's state of mind and intent to kill. (People v. Lashley (1991) 1 Cal.App.4th 938, 945-946 ["One who intentionally attempts to kill another does not often declare his state of mind . . . ."].)