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'.