This is another case that circles around 4th Amendment rights, but involves a tradeoff between a philosophical value that we "want" to support against a logistical constraint that can tie our hands.
The issue revolves around whether police need to get a warrant if a DUI suspect refuses to get a blood test.
Philosophically, we want to require the authorities to get a warrant if ever they want to do something intrusive, and hauling a suspect down to a clinic and drawing blood is certainly intrusive. But the problem is that the suspect can refuse to voluntarily cooperate and by the time the police can get a warrant, the suspect's blood alcohol level has gone down.
So which wins - our design to protect the public from police intrusion or the logistical constraint that the blood has to be tested quickly? Sometimes we are forced to pick one or the other. These are tough because how to we compare two options where the benefits are on completely different dimensions (values versus practicality)?
But here, we might be able to come up with a solution that satisfies both needs. What if we have some kind of expedited process to get a warrant? The person giving the warrant can't be associated with the police or we lose the ability to prevent the police from harassing those they don't like. But a judge might not be accessible late at night when DUIs are often stopped.
Perhaps some kind of 3rd party? Who would fit? Qualified to decide and available at 3am. Hmmm
Another option would be the exception principle. We could let police force the issue at first, but any officer or station that has a high rate of doing this would be required to get a full warrant from that point on. This penalty should be steep enough to deter most officers from being too aggressive.