Who does the detective leading the murder investigation turn out to be?

The detective leading the murder investigation turns out to be Vincent's brother, which adds a complex layer to the narrative of "GATTACA." This revelation is significant because it intertwines personal relationships with professional duties, highlighting the theme of genetic identity versus personal identity. Vincent, who is a genetically engineered individual striving to overcome societal prejudice, must now navigate his relationship with his brother, who embodies both familial ties and the law. This familial connection intensifies the stakes of the investigation, creating tension between Vincent's desire to prove himself and his brother's role in enforcing the societal standards that deem Vincent inferior. The discovery that the detective is Vincent's brother complicates the emotional landscape of the story, ultimately reflecting the broader themes of family loyalty, genetic determinism, and individual aspirations in a society that values genotype over phenotype.