Time to find Keith McKinney and talk with this Robobrain. Head to the West and through the door there.
Talk with Keith and ask him about the murder and his thoughts on it. He will explain that he suspects Santiago because he keeps returning to the scene of the crime.
Talking with Gilda, if you flirt (and possibly sleep with her), she will openly share what she knows. Otherwise she will hint to getting to know you better. She will not give any answers until you go on a date with her or ask her about her acting career.