Who dunnit?

One of the most important clues at a crime scene investigation are latent fingerprints left behind by the criminal. No two fingerprints are alike - every individual has unique fingerprint ridges that do not change throughout one's lifetime. Over the years, forensic scientists have developed many ways to look at these fingerprints. Today, the most commonly used method is still fingerprint dusting where powder is spread lightly over a fingerprint surface using a brush, and clear tape is placed over the latent print in order to transfer and preserve the fingerprint pattern.

Scientists have developed special polymer films to improve the transfer of the fingerprint from the crime scene surfaces to the laboratory. This new polymer is conjugated with highly fluorescent particles so that interaction with oil would cause swelling and increased fluoresence intensity. This allows fingerprints to show up more clearly. Below are two fluorescent images showing (a) a fingerprint transferred to a polymer film from a glass surface and (b) the same fingerprint image after digital contrast enhancement.

Source: Chemical Communications
Image Sources: Teachcops Chemical Communications