[logfromblammo]

The person leaving with the money is not leaving with the necessary evidence that a crime has occurred. It is not illegal to carry money (most of the time).

You follow the guy with the drugs, so that you can seize the drugs and place them into evidence. That, combined with the LEO witness of the transaction, provides probable cause to get a warrant for the person who left with the money. You presumably also have the guy who left with the drugs in custody, and the prosecutor might be able to convince him to testify against the other party.

If you follow the guy with the money, the only evidence you have is the LEO witness testimony. As we have been repeatedly reminded in the smartphone age, that sometimes contradicts the objective evidence. (That is a polite way of saying that some cops lie in order to achieve a desired enforcement outcome.) The jury couldn't know for sure whether the cop saw a drug deal and decided to go after the "bigger fish", or whether he just saw a guy with a lot of cash and came up with a plausible pretext for taking it.

Cops should chase the hard evidence necessary to secure a conviction, not the potential forfeiture targets that pay for all those cop toys.

(Of course, there was no third option that might satisfy someone who opposes the continuation of the "war on drugs".)

[rday]

Very good point. I suppose the question is a false choice in the first place. The officer should just write down both tag numbers with a "worst drug deal ever" note...