Bullet casing image alignment and forensic analysis system using the same

A computer-implemented method comprising:

• obtaining a candidate image, the candidate image comprising a portion of a bullet shell casing including a plurality of features identifying of a firing process of a specific firearm that fired a bullet including the bullet shell casing;
• determining, for the candidate image, a rotation angle to rotate the candidate image to align the portion of the bullet shell casing with a target orientation, wherein the determining comprises:
• identifying, in the candidate image, a first feature of the plurality of features comprising a firing pin aperture impression on the bullet shell casing;
• determining, for the identified firing pin aperture in the candidate image, a shape of a plurality of shapes of the firing pin aperture impression;
• in response to determining that the firing pin aperture impression has a first shape of the plurality of shapes, selecting a first rotation angle to rotate the candidate image of the bullet shell casing to align the firing pin aperture impression with a first target orientation for the first shape;
• in response to determining that the firing pin aperture impression has a second, different shape of the plurality of shapes, selecting a second rotation angle to rotate the candidate image of the bullet shell casing to align the firing pin aperture impression with a second target orientation for the second shape;
• rotating the candidate image by the rotation angle comprising either the selected first rotation angle or the selected second rotation angle to produce a rotated candidate image;
• and
• providing the rotated candidate image.

A non-transitory computer storage media encoded with computer program instructions that when executed by one or more computers cause the one or more computers to perform operations comprising:

• obtaining a candidate image, the candidate image comprising a portion of a bullet shell casing including features identifying of a firing process of a specific firearm that fired a bullet including the bullet shell casing, wherein the features include firing pin aperture impression, scratch patterns, drag mark, and one or more breechface patterns;
• determining, for the candidate image, a rotation angle to rotate the candidate image to align the portion of the bullet shell casing with a target orientation using the features identifying of the firing process of the specific firearm that fired the bullet including the bullet shell casing, wherein the determining comprises:
• identifying, in the candidate image, a shape of a firing pin aperture impression on the bullet shell casing, comprising:
• in response to identifying that the firing pin aperture impression has a teardrop or rectangular/elliptical shape, selecting a first rotation angle to rotate the candidate image of the bullet shell casing to align the scratch patterns with a first target orientation;
• in response to determining that the firing pin aperture impression has a circular shape, determining whether a firing pin aperture shear is visible, comprising:
• in response to determining the firing pin aperture shear is visible, selecting a second rotation angle to rotate the candidate image of the bullet shell casing to align the scratch patterns at the first target orientation;
• and
• in response to determining the firing pin aperture shear is not visible, determining whether the drag mark is visible, comprising:
• in response to determining the drag mark is visible, selecting a third rotation angle to rotate the candidate image of the bullet shell casing align the drag mark with a second target orientation;
• and
• in response to determining the drag mark is not visible:
• identifying one or more breechface patterns on the bullet shell casing;
• and
• selecting a fourth rotation angle in response to the one or more breechface patterns to align at least one of the one or more breechface patterns with a respective, third target orientation;
• rotating the candidate image by the rotation angle comprising either the selected first rotation angle or the selected second rotation angle to produce a rotated candidate image;
• and
• providing the rotated candidate image.

A system comprising:

• one or more computers and one or more storage devices on which are stored instructions that are operable, when executed by the one or more computers, to cause the one or more computers to perform operations comprising:
• obtaining a candidate image, the candidate image comprising a portion of a bullet shell casing including a plurality of features identifying of a firing process of a specific firearm that fired a bullet including the bullet shell casing;
• determining, for the candidate image, a rotation angle to rotate the candidate image to align the portion of the bullet shell casing with a target orientation, wherein the determining comprises:
• identifying, in the candidate image, a first feature of the plurality of features comprising a firing pin aperture impression on the bullet shell casing;
• determining, for the identified firing pin aperture impression in the candidate image, a shape of a plurality of shapes of the firing pin aperture impression;
• in response to determining that the firing pin aperture impression has a first shape of the plurality of shapes, selecting a first rotation angle to rotate the candidate image of the bullet shell casing to align the firing pin aperture impression with a first target orientation for the first shape;
• in response to determining that the firing pin aperture impression has a second, different shape of the plurality of shapes, selecting a second rotation angle to rotate the candidate image of the bullet shell casing to align the firing pin aperture impression with a second target orientation for the second shape;
• rotating the candidate image by the rotation angle comprising either the selected first rotation angle or the selected second rotation angle to produce a rotated candidate image;
• and
• providing the rotated candidate image.