In 13th-century China, a field worker was killed with a sickle — and all villagers’ sickles were alike. So the investigator had every worker lay down his tool in a field, and observed that just one sickle attracted blowflies, which were known to seek out blood. Its owner, the culprit, immediately confessed. The Chinese sickle slaying is one of the first reported cases of forensic investigation. The role of science in evidence collection and presentation has only become more importan…