THE
SCIENCE
OF
FINGERPRINTS
Classification and Uses
UNITED STATES DEPARTMENT OF JUSTICE
FEDERAL BUREAU OF INVESTIGATION
John Edgar Hoover, Director
INTRODUCTION
This booklet concerning the study of fingerprints has been prepared bythe Federal Bureau of Investigation for the use of interested lawenforcement officers and agencies, particularly those which may becontemplating the inauguration of fingerprint identification files. Itis based on many years' experience in fingerprint identification workout of which has developed the largest collection of classifiedfingerprints in the world. Inasmuch as this publication may serve as ageneral reference on classification and other phases of fingerprintidentification work, the systems utilized in the IdentificationDivision of the Federal Bureau of Investigation are set forth fully.The problem of pattern interpretation, in particular, is discussed indetail.
Criminal identification by means of fingerprints is one of the mostpotent factors in obtaining the apprehension of fugitives who mightotherwise escape arrest and continue their criminal activitiesindefinitely. This type of identification also makes possible anaccurate determination of the number of previous arrests andconvictions which, of course, results in the imposition of moreequitable sentences by the judiciary, inasmuch as the individual whorepeatedly violates the law finds it impossible to pose successfullyas a first, or minor, offender. In addition, this system ofidentification enables the prosecutor to present his case in the lightof the offender's previous record. It also provides the probationofficers, parole board, and the Governor with definite informationupon which to base their judgment in dealing with criminals in theirjurisdictions.
From earliest times fingerprinting, because of its peculiaradaptability to the field, has been associated in the lay mind withcriminal identification to the detriment of the other useful phases ofthe science. However, the Civil File of the Identification Division ofthe Federal Bureau of Investigation contains three times as manyfingerprints as the Criminal File. These civil fingerprints are aninvaluable aid in identifying amnesia victims, missing persons andunknown deceased. In the latter category the victims of majordisasters may be quickly and positively identified if theirfingerprints are on file, thus providing a humanitarian benefit notusually associated with fingerprint records.
The regular contributors who voluntarily submit fingerprints to theFederal Bureau of Investigation play a most important role in the[Pg iv]drama of identification. Their action expands the size of thefingerprint files, thereby increasing the value of the files to alllaw enforcement agencies. Mutual cooperation and efficiency areresultant by-products.
The use of fingerprints for identification purposes is based upondistinctive ridge outlines which appear on the bulbs on the inside ofthe end joints of the fingers and thumbs. These ridges have definitecontours and appear in several general pattern types, each withgeneral and specific variations of the pattern, dependent on the shapeand relationship of the ridges. The outlines of the ridges appear mostclearly when inked impressions are taken upon paper, so that theridges are black aga