This chapter describes a method used by fingerprint examiners to determine a print's source by viewing and comparing the general ridge flow in two fingerprints; the sequences and configurations of ridge paths; and if needed, the sequences and configurations of morphological details of a particular ridge and nearby ridges.
The chapter also addresses the philosophies of perception and decisionmaking that all fingerprint examiners must understand before turning to the mechanics of a comparison. Following the chapter's introduction, the following topics are discussed in sequence in the chapter's major sections: "Fundamentals of Comparison;" "ACE-V Examination Method;" "Decision Thresholds;" "The Examination;" and "Simultaneous, Adjacent, or Aggregate Fingerprints." In summary, the chapter notes that an expert conducts an examination based upon knowledge and beliefs from training, experience, understanding, and judgment. An acceptable explanation of a method for documenting expert perception is analysis, comparison, and evaluation, as well as the demonstration of repeatable determinations with verification. A threshold, based on unique detail and expertise, is used to make decisions throughout the examination process. Quality of details of unique features of the source requires a corresponding quantity of details to go beyond doubt to sufficiency in the QQ (quantitative-qualitative) threshold. Likewise, quantity of details of unique features of the source requires a corresponding quality of details to go beyond doubt in the QQ threshold. The examiner must ask and correctly answer all relevant questions in order to reach the proper conclusion. The examiner is involved in a process that moves from not knowing, through the imitation of doubt, to knowing and believing. Scientists should collaborate in order to improve explanations of the foundations and processes examiners experience when making judgments throughout this process. 15 figures and 16 references