I'm genuinely surprised to learn that sobriety checkpoints are considered to violate 10 states constitutions, including Washington's. I wonder if this has any impact on the rate of impaired driving in these jurisdictions
Do you mean in the sense that "we find more impaired drivers because we look" or "we find fewer impaired drivers because of threats"? According to the top hit on Google for "washinton state dui rates" Washington is still top 10 [1]. I can't really speak to what a good source for these statistics might be, though.
[1] https://www.injurytriallawyer.com/blog/washington-state-dui-...