People v. Agnelli, JAD21-05

Defendant Dustin Agnelli was charged with using an electronic tracking device (Pen. Code §637.7(a)) after a magnetic tracker was found on a Nissan Altima co-registered to him and the victim.
The victim—who did not consent—found the device on the car and reported it; Agnelli admitted the device was his and that he placed it to locate the vehicle.
Agnelli and the victim were co-registered owners; Agnelli claimed he (as a registered owner) consented to placing the device, while the victim did not.
At trial defense argued §637.7(b)’s consent exception was unclear when a vehicle has multiple registered owners; the jury asked whether one or all co-owners must consent, and the trial court said it could not clarify the law.
The jury convicted Agnelli under §637.7(a); the court placed him on informal probation.
On appeal the People conceded the conviction should be reversed; the Court of Appeal held the statute, as applied to Agnelli (a co-owner who consented while the other co-owner did not), is unconstitutionally vague and reversed the conviction.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether Penal Code §637.7(a) is unconstitutionally vague as applied where a vehicle has co-registered owners and only one owner consented to a tracking device	People prosecuted under §637.7(a); asserted statute prohibits use of tracking devices and did not successfully establish that all co-owners must consent (and ultimately conceded on appeal)	Agnelli argued the statute is vague as applied because it does not specify whether consent by one registered owner suffices when there are co-registered owners	The court held §637.7(a)/(b) is impermissibly vague as applied in this factual context because it fails to clarify whether all registered co-owners must consent; conviction reversed

People v. Health Laboratories of North America, 87 Cal.App.4th 422 (2001) (de novo review applies to statutory interpretation and constitutionality questions)
People v. Morgan, 42 Cal.4th 593 (2007) (distinguishes facial and as-applied vagueness challenges)
People v. Nguyen, 212 Cal.App.4th 1311 (2013) (framework for evaluating as-applied vagueness challenges and fair-warning doctrines)
People v. Abbate, 58 Cal.App.5th 100 (2020) (due process vagueness requirements described)
People v. Maciel, 113 Cal.App.4th 679 (2003) (statute must give definite guidelines to avoid arbitrary enforcement)
Chapman v. California, 386 U.S. 18 (1967) (constitutional harmless-error standard)
People v. Watson, 46 Cal.2d 818 (1956) (state standard for prejudice/harmless error)