No, they can free stop them all. They are limited to using evidence found on 3/4 of them.
I think Thomas has the correct logic, but Sotomayor came to the correct conclusion. To quote Thomas:
In principle I agree with this, but in practice, some drugs and drug paraphernalia sets the bar far too low in my opinion. If they can prosecute for drug possession, a victimless crime, then they can prosecute for literally anything found; the deterrent effect is always going to be higher than the cost of exclusion. I could see this for evidence of DUI, murder, rape, terrorism, child molestation/endangerment/pornography - things which result in great personal or societal harm or reasonable potential harm - but here the charges and thus the presumed societal damage are relatively minor. It's yet another assault on the Fourth Amendment - it might LOOK minor, but it's certainly going to have a widespread effect on the Fourth by letting cops know that even if the reason for the stop is bullshit, they can still make arrests stick.
Thank you for actually discussing the legal issues here, although I do not believe that your conclusion is correct.
There is a good bit of discussion about the purpose and flagrancy of the stop, which is relevant.
For example:
The proposed conduct you are responding to would be flagrant, illegal, and expose police to civil liability. Understanding this and reasonable suspicion in this case is very important to understanding our rights. Even if a stop is deemed illegal by the court, we ought to have more discussion about what makes it illegal and how that changes (or should or should not) what happens subsequently.
Again, I do not believe this to be the case. Such an arrest cannot stick unless there is an attenuating factor for the illegal stop. In this case, it's the arrest warrant. Another example might be a man illegally stopped then pulling a gun on the cop. The cop has PC then to arrest the person and those charges will stick, including possession charges for illegal drugs found on searching the man after the arrest despite the initial stop being illegal.
I agree that there is quite a difference in possession of drugs and other products of searches in this case, and it may mean that the standard for exclusion should be tighter.
This reminds me of the time when the inimitable Mulla Nasrudin was made a judge. After the prosecution presented its case the Mulla banged down the gavel and announced, I think you are right. The defense leapt to its feet and presented its case, to which the Mulla again banged down the gavel repeating I think you are right. The Forman of the jury exclaimed, they can't both be right, to which the Mulla replied, I think you are right.
He who makes a man a judge, destroys him. A saying.
What I hear in the two opinions above is a suspicion in one that our legal system will provide real justice and in the other a faith that it will.
The extent to which any system can approximate justice depends, heavily, in my opinion, on the quality of the souls making the decisions as to what it is.
As in all things, the degree to which the idealism of liberal values win out over the realities of life experiences that create a factual foundation for cynicism, depend on the normative experiences like a bell curve, that the average person in a society experiences.
I would say that the quality and degree of evolution a society can attain and maintain depend of how positively the average man sees his future.
The way I assess the greatness of an individual is by the quality of his ideals. This is why I greatly admire the Buddhist whose prayer is. I vow to save all sentient beings.