What does Jerome (Vincent) leave behind at the murder scene?

In the context of GATTACA, Jerome (Vincent) leaves behind an eyelash at the murder scene. This detail is significant because DNA can be extracted from such sources, enabling forensic investigators to identify individuals based on their genetic makeup. The film explores themes of genetic identity and the implications of genetic discrimination, and the eyelash serves as a crucial piece of evidence linking Jerome to the crime scene. The other options, while they might contain DNA as well, do not carry the same weight in the narrative, as the lost eyelash directly aligns with the film's emphasis on genetics and how easily one's identity can be traced back through seemingly minor biological materials. This event underscores the tension between genetic manipulation and the inherent unpredictability of human life, which is a central theme throughout the story.