> Researchers analyzed coroner records from Montgomery County in Ohio from January 2019 to September 2024, focusing on 246 deceased drivers who were tested for THC following a fatal crash.

This paper would need to go into way more detail to be at all useful.

40% is a staggering number, which makes me suspect that all it measures is Montgomery County police's pretty good track record for deciding when to test someone for THC during an autopsy