Comparison microscope

[1] In 1929, using a comparison microscope adapted for forensic ballistics, Calvin Goddard and his partner Philip Gravelle were able to absolve the Chicago Police Department of participation in the St. Valentine's Day Massacre.

Philip O. Gravelle, a chemist, developed a comparison microscope for use in the identification of fired bullets and cartridge cases with the support and guidance of forensic ballistics pioneer Calvin Goddard.

[2] Sir Sydney Smith also appreciated the idea, emphasizing its importance in forensic science and firearms identification.

Despite this evolution, however, the basic tools and techniques have remained unchanged which are to determine whether or not ammunition components were fired by a single firearm based on unique and reproducible microscopic and class characteristics, or to reach a "no conclusion" result if insufficient marks are present.

[3] Since, ballistic identification has benefited from a long series of structural, scientific and technological advances, law enforcement agencies have established forensic laboratories and researchers have learned much more about how to match bullets and cartridge cases to the guns used to fire them, and comparison microscopes have become more sophisticated.

Forensic innovator Calvin Goddard offered ballistic identification evidence in 1921 to help secure convictions of accused murderers and anarchists Nicola Sacco and Bartolomeo Vanzetti.

A worldwide outcry arose and Governor Alvin T. Fuller finally agreed to postpone the executions and set up a committee to reconsider the case.

By this time, firearms examination had improved considerably, and it was now known that a semi-automatic pistol could be traced by several different methods if both bullet and casing were recovered from the scene.

Goddard used Philip Gravelle's newly invented comparison microscope and helixometer, a hollow, lighted magnifier probe used to inspect gun barrels, to make an examination of Sacco's .32 Colt, the bullet that killed Berardelli, and the spent casings recovered from the scene of the crime.

Colonel Goddard was the key forensic expert in solving the 1929 St. Valentine's Day Massacre in which seven gangsters were killed by rival Al Capone mobsters dressed as Chicago police officers.

It also led to the establishment of the United States' first independent criminological laboratory, which was located at Northwestern University and headed by Goddard.