Class characteristics of friction ridge prints are those characteristics that can be possessed by more than one print. Even though a class characteristic may be possessed by millions of prints, it can still be of value to the individualisation or identification process. This is so because such characteristics reduce the population of prints that must be effectively eliminated before a condition of identity or common source for two prints can be stated with certainty.
The class characteristics of friction ridge skin extend to many factors other than digit or palm, or toe or sole, and the definable pattern type. Patterns of the same type, by definition, may appear quite different. Thus it is not necessary to consider only whether a pattern is a loop, for instance, but also the size of the loop, the presence or absence of converging ridges, the ridge count, the degree of the slope of the pattern, and even the amount of curvature that may be present.
The individualising characteristics of friction skin are those features of the ridges which make it possible to characterise or identify a particular print as having been made by a particular person. These characteristics are considered with respect to their location, general appearance, orientation, and interrelationship when comparison is made between two prints.
In fingerprinting, classification and identification are distinct concepts. The two functions may and often are performed by different personal. In some police departments, the division of labour may be so sharp that a person skilled in fingerprint classification may not be qualified to identify suspects based on fingerprint examinations. The examination may be conducted manually or by computer (AFIS) followed by visual comparison.