i. Measurable features of a specimen that indicate a restricted group source. They result from design factors and are therefore determined before manufacture. In the context of this module, general rifling characteristics of the barrel of a firearm are the class characteristics of interest.

i. Marks produced by the random imperfections or irregularities of tool surfaces. These random imperfections or irregularities are produced incidental to manufacture and/or are caused by use, corrosion, or damage. They are unique to a particular tool and distinguish it from all other tools. In the context of this module, the tool is the interior of the barrel of a rifled firearm.

• Significant because they relate to a smaller group source, that is, a subset of the class to which they belong

• Identifiable within a time frame since manufacturing processes change over time

A. The process of determining whether or not the striated toolmarks on two objects, such as fired bullets, correspond.

c. The changing environment of the courtroom following Daubert v. Merrell Dow Pharmaceuticals

d. The potential for increased credibility for examiners in the courtroom

1. The theory of identification as it pertains to the comparison of toolmarks enables opinions of common origin to be made when the unique surface contours of two toolmarks are agreement.

3. Currently, the interpretation of individualization/identification is subjective, founded on scientific principles and based on the examiner's training and experience.

• Recognizing corresponding patterns within impressed toolmarks

• Determining the best known non-match in their personal experience

1. Some agreement of individual characteristics and all discernable class characteristics, but insufficient for identification.

2. Agreement of all discernable class characteristics without agreement or disagreement of individual characteristics due to an absence, insufficiency, or lack of reproducibility.

3. Agreement of all discernable class characteristics and disagreement of individual characteristics, but insufficient for an elimination.

5. Other portions of fragmented, mutilated, or otherwise damaged bullets

6. Metallic fragments that cannot be identified as having been a part of a fired bullet (often the product of crime scene searches where all small metal items were collected).

1. The rifling in the barrel of a firearm bears unique microscopic characteristics due to manufacturing processes, use, and abuse.

2. These characteristics mark the bearing surfaces of bullets when fired through the barrel.

3. These individual characteristics are reproducible and identifiable with a particular firearm.

e. Determine if latent fingerprint examinations should be performed prior to toolmark examinations

f. Determine if other examinations (not requested) should be performed. If so, coordinate with the investigator.

• To determine if the firearm reliably reproduces microscopic marks on test fired bullets that are suitable for comparison purposes.

• To allow the examiner to assess the quality of marks produced by the firearm.

— Mark the test bullets and indicate the sequence in which they were recovered.

— Use a stereomicroscope to determine the presence and quality of microscopic marks on the test bullets prior to examination under the comparison microscope.

— Place one of the test fired bullets on the right stage of the comparison microscope. Attach the nose of the bullet to the mount.

—Adjust the lighting from the rear of the microscope to provide oblique illumination over the bearing surface of the bullet.

— Examine the entire bearing surface of the test bullet using low magnification (10x-20x) to determine the best area of individual characteristics. When such an area is located, leave the right stage in that position.

— Place a second test bullet on the left stage with the nose in the same direction as the bullet on the right stage.

— Rotate the bullet on the left stage looking for the same area of individual characteristics as on the bullet on the right stage. The entire surface of the bullet should be considered. Higher magnifications should be used to verify the correspondence of finer striations.

— If an area of correspondence is found, align the land or groove impressions and rotate both bullets simultaneously. Examine and compare each land impression and each groove impression area from base to nose until a conclusion can be drawn that there is or is not sufficient agreement for identification.

◊ Agreement is sufficient when it exceeds the best level of agreement demonstrated between bullet striations known to have been produced by different barrels (the best known nonmatch).

◊ If an identification cannot be made between the test bullets (there is not sufficient agreement), then more test bullets should be fired and compared. If an identification still cannot be made, the examiner may reach the conclusion that the barrel of the firearm in question does not consistently produce sufficient individual marks to warrant an identification.

◊ If an identification can be made, the area of best agreement or the area with the most obvious striations should be indexed with a permanent marker at the base and nose for later use in comparisons with evidence bullets. Indexing allows an examiner to quickly return to an area of correspondence.

• Use a stereomicroscope to determine that the recovered evidence bullet has microscopic marks of value and is suitable for comparison.

• Use the comparison process described previously to confirm that the test bullets from the recovered firearm can be identified with each other.

• Place the best test bullet on the right stage of the comparison microscope. Attach the nose of the bullet to the mount.

• Place the recovered evidence bullet on the left stage of the comparison microscope. Attach the nose of the bullet to the mount.

• Adjust the lighting equally from the rear of the microscope to provide oblique illumination over the bearing surface of both bullets.

• Rotate the test bullet, placing the previously marked index area in the center of the viewing area.

∆ If the widths of the observed impressions are not significantly different, the examination should proceed.

∆ If the recovered evidence bullet is damaged or deformed in the area previously indexed on the test bullet, it may be necessary to use other areas of the test bullet to compare to the undamaged areas of the recovered evidence bullet.

∆ If there is sufficient agreement for identification, the recovered evidence bullet should be indexed in the same area as the test bullet, even if this is a damaged area.

∆ If the recovered evidence bullet is missing the area indexed on the test bullet, the best area for comparison on the recovered evidence bullet should be indexed with a different color. The test bullet must be indexed again in the area of agreement and with the same color as used on the recovered evidence bullet.

∆ Document the area of agreement according to laboratory protocol.

° The recovered evidence bullet and the test bullet were fired from different firearms.

° Damage occurred to the recovered evidence bullet that caused distortion, deformation, or eradication of microscopic detail.

° The type of test ammunition was different from the recovered evidence bullet.

° Corroded deposits were dislodged from the barrel during firing, causing significant changes in the barrel.

° The firearm was damaged during the time interval between firing the recovered evidence bullet and the test bullet.

° Some or all chambers in a revolver are misaligned, causing differences in the microscopic marks found on bullets fired from different chambers.

° Remount both bullets on their respective bullet mounts and reexamine.

° Clean the barrel of the evidence firearm and obtain new test bullets. Bullets tested before and after cleaning must be retained.

° Such a difference could be due to deformed, damaged, or mutilated evidence bullets. If significant damage is not present, laboratory protocol for elimination should be followed (many laboratories require a minimum difference of 0.005 for elimination).

• Use a stereomicroscope to determine that the recovered evidence bullets have microscopic marks of value and are suitable for comparison. Group the bullets according to levels of damage and/or the amount of individual characteristics.

• Place the best bullet on the right stage of the comparison microscope. Attach the nose of the bullet to the mount.

• Adjust the lighting from the rear of the microscope to provide oblique illumination over the bearing surface of the bullet.

• Examine the entire bearing surface of the bullet using low magnification (10x-20x) to determine the best area of individual characteristics. When such an area is located, leave the right stage in that position.

• Place a second evidence bullet on the left stage. Attach the nose of the bullet to the mount.

• Adjust the lighting from the rear of the microscope to provide oblique illumination over the bearing surface of the bullet.

° Such a difference could be due to deformed, damaged, or mutilated evidence bullets. If significant damage is not present, laboratory protocol for elimination should be followed (many laboratories require a minimum difference of 0.005 for elimination).

∆ If the widths of the observed impressions are not significantly different, the examination should proceed.

∆ If there is sufficient agreement for an identification, both recovered evidence bullets should be indexed.

° These examinations should be made with the bullets in phase. This means that the edges of the land and groove impressions of both bullets align with each other and the relationship of the other land and groove impressions in the viewing area is the same.

° If either of the bullets are damaged or mutilated, this may not be possible.

° Agreement is sufficient when it exceeds the best level of agreement demonstrated between bullet striations known to have been produced by different barrels (the best known non-match).

° Damage occurred to the bullets that caused distortion, deformation, or elimination of microscopic detail.

° Remount both bullets on their respective bullet mounts and reexamine.

– It may be necessary to use more than one evidence bullet to establish a chain of identifications within a set of submitted bullets. Recovered evidence bullets may be damaged, precluding examination of some land and groove impressions. Examination of different areas of these bullets may be necessary to link all the recovered evidence bullets.

i. NIBIN-related high-probability associations (hits) made in a remote laboratory that must be physically examined using a comparison microscope,

ii. routine liaison with examiners from other jurisdictions concerning possibly related cases,

iii. information provided to investigators by an informant indicating possible case linkages between cases from different jurisdictions.

i. chain of custody concerns (integrity of evidence) on the part of investigative agencies and prosecutors offices,

ii. policies relating to the shipment or transport of evidence to other laboratories or jurisdictions,

iii. budgetary constraints regarding long distance travel to other jurisdictions.

a. Mix the components of the casting material until the mixture begins to harden.

b. Apply the mixture to the surface of the fired bullet and allowed to completely harden.