If one bit of evidence was collected illegally, does that mean an entire case must be thrown out?
No. Even if some unlawfully uncovered evidence is excluded, the defendant may still be convicted based on other evidence. And there are exceptions to the rule. For example, when unlawfully seized evidence would have been obtained anyway, that evidence may be used. Nevertheless, in some cases, a guilty defendant will go free. For example, a drug user will go free when the drugs found on his person (the only evidence against him) were found as the result of an unlawful search.
