There are so many cases from which to choose. One of the most famous cases where little pieces of evidence made a big difference concerns the case of serial killer Ted Bundy. The FBI estimates that he killed over thirty people before he was captured. However, because he was clever, he was able to escape and evade the law.
But in 1978, he was captured and put in prison to face death through two pieces of evidence. First, there was a bite mark on a victim (Lisa Levy), which matched his distinctive teeth pattern. Second, there was also fibers found in his van, which matched the clothing of another one of his victims. Through these two pieces of evidence, he was sentenced and put to death in 1989.
In conclusion, forensic evidence, even of the smallest details can link a person to a crime beyond a shadow of dark.