OK, but that still doesn't explain why it's a "spectacularly bad idea" for police/DA to not bother prosecuting in cases like this. What exactly are they supposed to do when they don't have a cooperative victim? Why is it not-stupid for the victim to avoid the costs of an adversarial court case, but it's stupid for the DA to avoid a case that he or she is guaranteed to lose?
My Dad was a police officer for 41 years and, by chance, he is visiting me. I read him your comments. Based on his 41 years of extremely high level investigative experience (including lead investigator in more sexual assaults than he cares to remember) , you literally don't know what you're talking about. He laughed at your comment and said, "Wow, another asshole armchair investigator with no experience."
First, the DA in the American system is not guaranteed to lose. Rather, unless the alleged perpetrator is extremely wealthy, the DA has a tremendous advantage. This is unbelievably common knowledge and something he picked up working closely with FBI and DEA agents.
Second, when you don't have a cooperative victim, a skilled investigator will investigate why. Often this happens because either the perpetrator made a very graphic threat and/or the victim suffers from post traumatic stress disorder. In this case, a highly skilled investigator would make sure that the victim had access to the best victim services people around.
Further to that, a skilled investigator/prosecutor combination will take steps to shield and protect the victim from an adversarial system. One common method would be to overcharge, announce they're going for a max sentence and plea down to avoid trial, while still guaranteeing a sentence, probation and sex offender registries.
There is your precious answer. Now, take some time to evaluate what kind of heartless asshole calls a victim 'stupid'.
