CHEMICAL VAPOUR

Greymouth Evening Star, 11 August 1936, Page 12

CHEMICAL VAPOUR

AROUND FLEEING CRIMINAL.

LOS ANGELES, June 24.

Sensitive iodine vapor, “picking up” fingerprints from apparently blank surfaces, is being hailed by police officers as the latest if not the greatest single improvement in the technique of crime detection. Three ghosts of wayward hands have yielded their secret to Dr. John McMorris, Pasadena chemist, who recently presented his invention to the detective •world at the California State Division of the International Association of Identification.

The circle of surfaces susceptible to finger impressions is thereby widened to include bits of almost any kind of cloth, greasy surfaces and others which have defied the universal powder methods of “bringing up” finger prints.

Dr. McMorris discovered the affinity of iodine vapor for oil from human pores. He rigged up a device of chemistry tubing and found that the invisible pattern attracted iodine fumes in outline identical with the fingerprint betrayed by ever-escaping oil. The print is transferred for photographing to a silver sheet pressed for a second or two upon the telLtale surface. At first invisible on the silver, the print is “developed” by exposure to sun rays or similar light. A chemical reaction is responsible for the transfer.

TUBE CONTAINS CRYSTALS. Dr. McMorris’ tubing lias two bulges —one contains calcium chloride crystals over which the detective’s breath passes on its way to iodine crystals, held by glass in the second bulb. The warm breadth conveys the iodine vapor to the suspected surface . The new field of prints aa-e called latent, being formed by the pore oil rather than by the finger ridgjes under pressure upon a pattern medium. These former stay fresh at least 24 hours, usually long enough for inspection in the average crime case, whether it be for examining a ransom letter-or-a-waJl a criminal hugged while eluding police. Dr. McMorris credits William W. Harper, the first Pasadena police science consultant and. other Pasadena department officers, for his formula, “because they told me what the problem was and kept encouraging me to solve it.”