By a canal in Amsterdam's red-light district, one of the "window women" is actually a hologram which Dutch police hope will help solve the gruesome murder of a sex worker in 2009. "15 years ago Betty was killed in a horrible way, and the investigation was never actually closed," Amsterdam police spokesman Olav Brink says. In the streets of De Wallen, groups of locals and visitors pause and strike up conversations about the unusual display: "the hologram was really effective in a way that it made it real" says Soyoon Jun, who lives near the red-light district. IMAGES AND SOUNDBITES