At his peak, Guzmán ran an organization that moved industrial quantities of cocaine, heroin, methamphetamine, and marijuana across hemispheres — a logistics operation that law enforcement agencies spent decades attempting to dismantle. He escaped from maximum-security Mexican prisons twice before his eventual extradition, and the violence attributed to his cartel's territorial conflicts accounts for a death toll in the tens of thousands. His rise traced a familiar arc through the narco hierarchy — route mapper, logistics supervisor, lieutenant — before he broke off to build the Sinaloa Cartel into what authorities described as the world's most powerful drug trafficking organization.

Her victims included a husband, a son, and a boyfriend — a pattern of harm that unfolded across more than a decade before investigators began connecting the deaths. Arsenic poisoning, collected insurance payouts, and a car bombing tied together a case that made her the first woman executed in Florida in over a century.

Fourniret operated for over fifteen years before his arrest, preying primarily on young women and girls across France and Belgium with the active knowledge of his wife. The partnership between the two — and Olivier's eventual decision to inform on him — made the case unusual among serial killer investigations of its era. His confessions came in stages over years, with victims' families waiting long after his 2003 arrest to learn the fates of those he had killed.

Puente operated within a structure of care and dependency, turning a boarding house for elderly and mentally disabled tenants into the mechanism of her crimes. The financial motive — collecting Social Security payments from those she had killed — is what drove the pattern of murders across six years, and what ultimately drew investigators' attention. The case remains notable for how thoroughly ordinary circumstances concealed what was happening at the Sacramento property.