"In R.V. Campbell, 2024 SCC42, Guelph police officers arrested a known drug dealer, Kyle Gammie, for trafficking and lawfully seized a cellphone he tossed into a car during the arrest.
Following the arrest, four text messages lit up the phone's screen. They appeared as an offer to sell drugs."
The officers suspected the drugs were heroin laced with fentanyl. The officers were concerned the drugs were primed to hit the streets immediately, with deadly consequences.
Without a warrant the officers replied to the texts, impersonating Gammie. When the sender-Dwayne Campbell-appeared at Gammie's apartment to sell the drugs he was arrested.

Here is the Dumb Criminal part.
In court, Campbell testified that he did not send the incriminating texts, but willingly admitted that he sent other texts which arranged the sale and delivered the drugs.
"In essence, Campbell claimed he as acting as the drug courier to facilitate the drugs."
Here is Mike Novakowski's analysis of the case.
https://www.blueline.ca/case-law-using-seized-cellphone-to-impersonate-drug-dealer-deemed-lawful/