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Strengthening Forensic Science in the United States: A Path Forward
Development technique—chemical signature of the technique and consistency of the chemical signature across the impression.
Capture technique—photograph (digital or film) or lifting material (e.g., tape or gelatin lifter).
Size of the latent print or the percentage of the surface that is available for comparison.
The examiner also must perform an analysis of the known prints (taken from a suspect or retrieved from a database of fingerprints), because many of the same factors that affect the quality of the latent print can also affect the known prints.
If the latent print does not have sufficient detail for either identification or exclusion, it does not undergo the remainder of the process (comparison and evaluation). These insufficient prints are often called “of no value” or “not suitable” for comparison. Poor-quality known prints also will end the examination. If the examiner deems that there is sufficient detail in the latent print (and the known prints), the comparison of the latent print to the known prints begins.
Visual comparison consists of discerning, visually “measuring,” and comparing—within the comparable areas of the latent print and the known prints—the details that correspond. The amount of friction ridge detail available for this step depends on the clarity of the two impressions. The details observed might include the overall shape of the latent print, anatomical aspects, ridge flows, ridge counts, shape of the core, delta location and shape, lengths of the ridges, minutia location and type, thickness of the ridges and furrows, shapes of the ridges, pore position, crease patterns and shapes, scar shapes, and temporary feature shapes (e.g., a wart).
At the completion of the comparison, the examiner performs an evaluation of the agreement of the friction ridge formations in the two prints and evaluates the sufficiency of the detail present to establish an identification (source determination).21 Source determination is made when the examiner concludes, based on his or her experience, that sufficient quantity and quality of friction ridge detail is in agreement between the latent print and the known print. Source exclusion is made when the process indicates sufficient disagreement between the latent print and known print. If neither an identification nor an exclusion can be reached, the result of the comparison is inconclusive. Verification occurs when another qualified examiner repeats the observations and comes to the same conclusion, although the second examiner may be aware of the conclusion of the first. A more complete de-