The use of forensic ballistics for crime scene investigations was first formally established in 1923 with the creation of the independent Bureau of Ballistic Forensics in New York City, by Charles Waite, Calvin Goddard, John Fisher and Phillip Garavelle.
The Bureau developed a comparison microscope that had an optical bridge, allowing two items to be compared at the same time. Striation patterns are distinct to each gun barrel and leave markings on any bullet fired through it. The comparison microscope allowed for direct examination of two slugs making it easier to match the striation pattern. The Bureau also developed the helixometer, which was a magnifying device for examining the inside of gun barrels and accurately measuring the pitch of the rifling.
The first use of forensic ballistics in a court of law took place in 1927, at the murder trial of Sacco and Vanzetti. The accused murderers were convicted on the testimony of Calvin Goddard that one fatal bullet was fired from Sacco's gun. The pair were executed the following year. Calvin Goddard's findings were re-examined in 1961 and 1983 and were verified both times.
The tools of forensic ballistics have advanced with technology, including the development of the confocal microscopy 3-D bullet-imaging systems in 2005, but they are still used to match the gun barrel's striation to that of a fired bullet.