Justice Dalila Dewar wrote for a unanimous court that while officers may stop vehicles for observed violations, such seizures must be conducted in a reasonable manner. The court held the 24-hour gap here unreasonable because the record did not explain why the officer departed from his regular practice of radioing for a marked cruiser right away.
Officer Mathew Pieroway was conducting drug surveillance in an unmarked vehicle on March 27, 2019, when he saw Arias pull his SUV to the right of a line of stopped vehicles, fail to stop at a stop sign, and turn left in front of the line. Pieroway did not attempt a stop that day.
The next day, during continued surveillance, Pieroway radioed for a marked cruiser, saying officers were "looking to stop a vehicle for [a] drug investigation." The stop produced cocaine on Arias's person and in his vehicle.
Pressed on why he had not called for a marked cruiser immediately after the violation, the officer gave a one-word reply: "safety." The court found that answer insufficient, rejecting the Commonwealth's argument that safety concerns justified the delay.
The opinion emphasized that the elapsed time between an observed violation and a subsequent stop must be reasonable on the totality of the circumstances, and that the passage of time increases the possibility of arbitrary police conduct. The court set no specific time limit but required that delays be justified by the circumstances.
The decision builds on the court's 2022 ruling in Commonwealth v. Daveiga, which held that police authority to conduct traffic stops has limits. The Arias court extended that principle to delayed stops and added that a parallel drug investigation does not justify postponing a stop for an observed traffic violation.
Arias had been charged with trafficking 200 or more grams of cocaine and, after a mistrial and charge reduction, was convicted of trafficking 18 to 36 grams. The Superior Court had denied his motion to suppress, citing the absence of Massachusetts case law on stops based on prior-day violations. The SJC reversed that denial, vacated the conviction, and remanded to the Superior Court.