Beginning on April 22, 1942, Minneapolis Police Detectives attended 10 days of instruction in advanced methods of crime detection.
The course was conducted by FBI agents and it took place at the Bryant Avenue Station. The course was focused on detection during war emergencies, especially in the event of bombing.
Detectives learned how to discern whether a window was broken from the inside or the outside and also how to thwart attempts to collect insurance illegally.
They viewed and received instruction from film footage taken of emergency police work executed in London during bombing raids.
In the photograph above (from L to R), FBI Agent W.M. Sirene is instructing Detectives George Barry and H.W. Holmquist in the finer points of fingerprinting.
Source: Minneapolis Tribune of April 22, 1942