With FP and FN you really need to be careful... 1 person committed a crime. So the true positive rate is 1 out of 7 billion or so. So how many false positives

With FP and FN you really need to be careful... 1 person committed a crime. So the true positive rate is 1 out of 7 billion or so. So how many false positives would 0.1% lead to? About 7 million pants wearers? And for false negatives, we expect half the time the true criminal's pants would prove them innocent? I don't think you can really trust evidence if the true criminal has a coin-flip chance to show innocence with it.