Screening is not 100% accurate. It's based on a questionnaire. We ask people questions and how they respond isn't always 100% truthful. Sometimes they minimize things, and so on.
Another thing is that somebody could be fine today, but at the end of the week their relationship is falling apart and they've got into trouble, and things could happen. They're good one day, but a few days later they might not be.
We have to be very careful to understand the limitations of screening. We do it and we believe it's important, but we cannot rely on it as our only defence mechanism. This is why we spend so much time on education. It's so that people come forward for care when they need it, because we can't screen people every day.