DUI checkpoints are absolutely terrible at catching dangerously drunk drivers. If the government really wanted to set up a checkpoint to catch dangerously-drunk drivers it could simply use some safety pylons construct a relatively-easy obstacle course and have cars drive through it. This would impede traffic flow somewhat, but far less than stopping motorists. It would require far less manpower than stopping every motorist, but would be more effective at catching dangerously-drunk drivers than stopping every fifth motorist.
But the Supreme Court isn't going to (or at least they shouldn't) look into the effectiveness of it, but merely the constitutionality. The effectiveness comes into the realm of the legislative branch (policy making) and the executive branch (implementation).
The complaint isn't merely that DUI checkpoints are ineffective, but rather that--given the manner in which they're conducted--many so-called "DUI checkpoints" are really nothing of the sort. There is no conceivable way in which having drug dogs sniffing cars at a "DUI checkpoint" will increase the effectiveness of the checkpoint in catching drunk drivers. The purpose of the checkpoints is to conduct unconstitutional fishing expeditions. Sticking a "DUI checkpoint" label on an unconstitutional drug checkpoint doesn't make it constitutional.
"There is no conceivable way in which having drug dogs sniffing cars at a "DUI checkpoint" will increase the effectiveness of the checkpoint in catching drunk drivers."
Good to see somebody debating worthwhile points. I agree with you. Drug checkpoints have been ruled unconstitutional by the US Supreme Court. The addition of drug-sniffing dogs is not germane to finding drunken drivers. In addition, opinions have led Court watchers to believe that the Superemes may rule against dogs if a case of merit gets the the SC. At this point, I believe that dogs have been allowed in past opinion ****(but importantly they haven't been germane to the facts of the case.) That will be one that I'll be interested in seeing when it comes.
"The purpose of the checkpoints is to conduct unconstitutional fishing expeditions"
The court has clearly ruled that checkpoints may not be set up to fish for general crime. They have to be set up for DUI or other specific warranted cases (like when in the DC metro area they set up checkpoints looking for fleeing felons etc)