J. F. McDonald was busy in his office at Tombstone, Arizona, when a long-distance call from Douglas sent him hurrying to that city.
On the night previous, the Phelps Dodge Corporation at Douglas, Arizona, was burglarized of about six thousand dollars' worth of platinum equipment. Before McDonald arrived on the scene, local authorities got to work and, from the clues at hand, decided it had been done by an "insider" employed in the laboratories.
Inasmuch as the Phelps Dodge robbery was one of a series of platinum robberies which were taking place at this time, the local authorities believed that a gang of robbers was at work, placing their "tools" in the laboratories as employes. An elaborate plan of shadowing was devised and certain persons were under grave suspicion.
Then McDonald arrived in Douglas. He did not visit the laboratory at once, as there were a number of so-called clues to follow. He spent the first day in following leads provided by the local police, but these led to nothing.
Then with the chief chemist, McDonald visited the laboratory. Fortunately, it had not been cleaned up since the robbery.
In securing the platinum, the thief had handled a number of glass beakers. On these were a number of finger prints, but the first attempts to develop them were in vain, as the powder failed to adhere to the glass. Examining them carefully, McDonald found they had been handled considerably, but the oil of the perspiration had been destroyed by the fumes of an acid solution to which the beakers had been exposed.
However, McDonald filled the beakers full of a solution of potassium permanganate in order to give the prints a black background. Then, without using a developing powder, he photographed the prints with good results.
McDonald's next step was to fingerprint all the laboratory workers. In no instance did he find a resemblance between the patterns on their fingers and those discovered on the glass beakers. This exploded the "inside job" theory and removed the suspicion from the innocent men who were blamed. The expensive process of shadowing, too, was eliminated, and the detectives were able to proceed constructively instead of wasting their efforts on false trails.
The entire West was circularized. The finger prints found on the glass beaker were sent to all police departments, and information sent to chemical buyers and all those likely to be approached by a platinum thief.
Nine days after the robbery, a man was arrested in San Francisco while trying to dispose of some platinum. McDonald's circulars had done their work. This man had in his possession over two-thirds of the platinum stolen from the laboratories in Arizona.
After confronting him with the finger-print evidence, Lieutenants Powell and Riehl of San Francisco obtained a confession from the man, who proved to be James Walker, a person connected with other platinum robberies.
Finger prints left on beakers during the burglary of the Miami Copper Company of Miami, Arizona, on September 22, 1922, proved Walker to have been the culprit in that case also. Sheriff Edwards of Gila County had preserved the finger prints for three years, when the mystery was cleared up by McDonald. Walker was also found to have been connected with the burglary in the laboratory of the New Cornelia Copper Company at Ajo, Arizona, on May 18, 1923. In each instance, these were thought to be "inside jobs" and innocent men suspected.
The discovery of Walker as the platinum thief who had been operating for three years in Arizona was a triumph for McDonald, as well as for the fingerprint system. In all this time the police had been working on false theories, following clues that led nowhere, engaging in the expensive process of shadowing and attaching suspicion to innocent laboratory workers. A few minutes after obtaining the finger prints on the beaker, McDonald had exploded all the "inside job" theories and started on investigations that really led to the discovery of the thief.
Walker pleaded guilty to his crimes, was sentenced to the Arizona State Penitentiary but later escaped.
1. "Daring Platinum Robberies Solved", Finger Print and Identification Magazine, Vol. 7, No. 9, March 1926, pages 16-17.