CHAPTER 16 FORENSICS
This chapter contains scientific and technical subjects and describes various technical skills and techniques required to develop the facts of an investigation.
LEARNING OBJECTIVES: Define some of the terms used in classifying or describing fingerprints. List the steps required to obtain good fingerprints. Explain how fingerprints are found, processed, and classified. Explain the importance of accurate fingerprint records.
Fingerprints are the most positive means of identifying individuals. The ridges on the skin of the palmae surfaces of the hands and the plantae surfaces of the feet are commonly referred to as papillary or friction ridges. These ridges form on the fetus before birth and remain unchanged throughout life, and even after death until decomposition of the skin destroys them. Damage to the skin during a person's life maybe either temporary or permanent. Abrasions and slight cuts that do not permanently affect the skin are corrected in time by nature, and the ridges reappear as they existed before the damage occurred. Deep cuts and injuries affecting the innermost sections of the skin will result in permanent scars but the general pattern will continue to exist.
The information given in this text is designed to assist you in applying correct fingerprinting techniques and processes in the field. It does not include procedures used to identify subjects by fingerprints, or the classification of fingerprints. Assistance required beyond the information contained in this text requires more technical considerations. You should seek such help from an investigation laboratory, or from others who are qualified as fingerprint classifiers with the Federal Bureau of Investigation (FBI) or with local civilian police organizations.
Some of the terms used in classifying or describing fingerprints are as follows:
Bifircafion- the forking or dividing of one ridge line into two or more branches.
Core- the approximate center of a fingerprint.
Delta- that point on a ridge at or in front of, and nearest the center of divergence of the type lines.
Divergence- the spreading apart of two ridges that have been running parallel or nearly parallel.
Focal points- the delta and core located within the pattern area of loops and whorls, and used to classify them.
Palmar- pertaining to palm impressions of the hand.
Plantar- pertaining to sole impressions of the foot.
Pattern area- that part of a loop or whorl in which appear the cores, deltas, and ridges, with which classification is concerned.
Point- a ridge characteristic formed by one of the three basic ridge characteristics-bifucation, ridge ending, or dot.
Ridge- elevated portions of skin that make the print. They result from the fusion of separate skin layers. Sweat pores run in single rows along the ridges and are deposited on a surface when a print is made.
Shoulders- the points at which the recurring ridge of a loop-type pattern definitely turns inward or curves.
Type lines- the two innermost ridges that start parallel, diverge, and tend to surround the entire pattern area.
The terms used in searching for or taking fingerprints include the following:
Latent print- used to describe all traces of prints found on items of evidence or at a crime scene. (The term was once used for invisible prints; however, modern police terminology uses it for all chance or unintentional prints.)
Record prints- inked finger, palm, and sole impressions obtained from a person for identification purposes. They may be obtained either directly from the person or from official files.
Major case prints- a complete set of record prints obtained from an individual, including, but not limited to, fingerprints, palm prints, edges of the hand, fingertips, and the entire finger. Major case pints are usually obtained in all investigations of serious offenses.