Can Drug Checking Save Lives? Evidence from Staggered Fentanyl Test Strip Legalization

Abstract

Illicitly manufactured fentanyl killed over 70,000 Americans in 2023, yet many states criminalized the test strips that could detect it. Between 2017 and 2023, 39 US jurisdictions legalized fentanyl test strips (FTS) through staggered decriminalization. I exploit this variation using a Callaway-Sant'Anna difference-in-differences design with CDC provisional mortality data. The simple aggregate ATT is 2.35 additional synthetic opioid deaths per 100,000 (SE = 0.55), but this estimate is fragile: randomization inference yields $p = 0.47$, HonestDiD sensitivity bounds include zero, and cohort-specific effects range from $-5.2$ to $+9.2$. The Sun-Abraham estimator finds no significant effect at any event-time horizon. I interpret these results as a precisely estimated null: FTS legalization alone neither meaningfully reduced nor increased overdose mortality during this period.