People v. Cady, 7 Cal. App. 5th 134

On Jan. 10, 2014, William Cady drove an SUV after drinking and using marijuana; he accelerated despite passengers' pleas and lost control, causing a rollover that killed three passengers and injured two.
Blood evidence showed BAC between 0.10–0.18 at the time of the accident (depending on absorption); toxicology showed recent cannabis with an expert opining an additive impairing effect with alcohol.
Cady was tried on counts including three counts of gross vehicular manslaughter while intoxicated (Pen. Code § 191.5(a)), and multiple Vehicle Code § 23153 injury counts: (a) alcohol only, (b) BAC ≥ .08, and (f) combined alcohol and drug influence.
The jury acquitted Cady of murder but convicted him of the manslaughter and DUI-related counts, finding multiple great-bodily-injury enhancements true; the trial court sentenced him to 18 years (with other counts stayed under § 654).
On appeal Cady argued (1) that count 7 (§ 23153(a) alcohol causing injury) is a lesser included offense of count 9 (§ 23153(f) combined influence), and (2) the trial court erred by not sua sponte instructing the jury on the lesser included offense vehicular manslaughter without gross negligence (Pen. Code § 191.5(b)) for counts 4–6.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether § 23153(a) (DUI-alcohol causing injury) is a lesser included offense of § 23153(f) (DUI combined alcohol+drug causing injury)	People: A conviction for combined influence does not necessarily include an alcohol-only conviction because the statutes differ by substance language; however, the People argued there are scenarios where combined-influence conviction can exist without alcohol-only guilt.	Cady: Conviction under § 23153(f) subsumes § 23153(a); convicting on both is barred as necessarily included offenses.	Held: Not a lesser included offense — combined influence can produce impairment when alcohol alone would not, so both elements are not identical.
Whether the trial court erred by not instructing on vehicular manslaughter (no gross negligence) as a lesser included offense of gross vehicular manslaughter (with gross negligence) for counts 4–6	People: No reversible error — defense invited the omission and evidence supported gross negligence, so no need for lesser instruction.	Cady: Court had sua sponte duty to give the lesser instruction; failing to do so was prejudicial.	Held: No error for two independent reasons — (1) defense counsel expressly and strategically declined the lesser instruction (invited error); (2) substantial evidence supported gross negligence so no lesser-included instruction was warranted; any error would be harmless.

People v. Sanders, 55 Cal.4th 731 (discusses rule against multiple convictions for necessarily included offenses)
People v. Reed, 38 Cal.4th 1224 (elements test for lesser included offenses)
People v. McNeal, 46 Cal.4th 1183 (definition and scope of "under the influence" in DUI context)
People v. Haeussler, 41 Cal.2d 252 (definition of "under the influence" — appreciable impairment standard)
People v. Shockley, 58 Cal.4th 400 (when trial court must instruct on lesser included offenses)
People v. Souza, 54 Cal.4th 90 (invited error and lesser-instruction principles)
People v. Horning, 34 Cal.4th 871 (invited error bars appellate challenge to instruction omission)
People v. Cooper, 53 Cal.3d 771 (what record shows a deliberate tactical choice for invited error)
People v. Watson, 30 Cal.3d 290 (standard for gross negligence and prejudice review standard for instructional error)
People v. D'Arcy, 48 Cal.4th 257 (considering counsel's concessions when assessing prejudice from instructional omissions)