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FBI Lab Case - December 1948

Did You Ever See
A Shoe Trap a Burglar?

A burglar has just rifled a building on a government reservation. He thinks he's clever. He has been most careful to cover up or to destroy the evidence. He was the smart aleck type. He felt certain that he would never leave any telltale tracks. He carefully removes the screen and steps out into the darkness. The soft earth below the window is his trap.

The next morning agents of the FBI investigating the burglary picked up a suspect. He denied his guilt. One of the agents noticed that his shoes were muddy. They also noticed that it had the appearance of the footprint left beside the building.

FBI Lab member examines the sole of the shoe
Examining the shoe.

In a matter of moments the plaster cast made at the crime scene and the shoes of the suspect are on their way to the FBI Laboratory in Washington.

First the examiner notes carefully the various characteristics in the plaster and compares them with the heel of the suspect's shoe.

He checks the reference collection of heel designs and studies further the characteristics which will be so important to his testimony. Yes, he feels certain that the shoe which left the impression in the earth is the shoe of the suspect.

In the meantime, the men in the Petrographic Section are making a further test. Soil clinging to the shoe has been carefully removed. It will be tested against the soil sent in by the agents, samples of the soil below the window. Preliminary checks under the microscope indicate that certain characteristics are present in both specimens of soil.

A test on the process refractometer
Using the refractometer.

Under high magnification the examiner notes the various crystalline materials. He also checks the reference collection of soil so that he might further study the characteristics.

Another test is made on the process refractometer and the examiner can now reach his conclusions. The report in confirmation of teletype goes out. Yes, the footprints match and the soil was from the same source. The FBI experts will testify to these facts.

From the FBI files, December 1948.