The Science of Fingerprints: Classification and Uses

by United States. Federal Bureau of Investigation

Portable articles removed should be labeled or marked so that they may be readily identified thereafter.

The beam of a flashlight played over the surface of an object will frequently show the location of latent impressions, although this is not an infallible test for their presence.

Evidence should be examined as soon as feasible after its discovery.

Following the location of any latent prints at the scene of a crime, the prints of all persons whose presence at the place under inspection has been for legitimate purposes must be excluded from further attention. It is advisable, therefore, during the initial stages of an investigation where latent prints are found, to secure the inked prints of all members of the household, the employees, and any police or other officials who may have touched the objects on which the latent impressions were found. Inked prints taken for this purpose are referred to as elimination prints.

Due to the fragmentary nature of most latent prints it is not possible to derive a classification which makes a file search practicable. A latent impression may be identified, however, by comparison with the prints of a particular suspect.

Inked fingerprints taken for comparison with latent impressions should be as legible and as complete as possible, including the areas not essential to classification, since identifications are often made with these areas. Inked palm prints taken should likewise be complete and clear and should include impressions of the finger joints. Persons not experienced in latent print comparisons should not attempt to evaluate latent fragments, since the area necessary for an identification may be extremely small compared to that of an average inked fingerprint.

Articles which are to be transported by mail or express should be so packed that the surfaces bearing latent impressions are not in contact with other surfaces. This may be accomplished by mounting the articles on a piece of fiber board or plywood. The board should then be secured in a box so that the objects will not touch or be shaken against the sides in transit. The package should be plainly marked "Evidence," to prevent inadvertent handling on opening. Cotton or cloth should never be placed in direct contact with any surface bearing latent prints.

Any number of paper or cardboard specimens may be placed in a single protective wrapper, since contact with other surfaces does not harm latents on such objects. Lifts, negatives and photographs are readily enclosed with letters.

An explanatory letter should accompany all evidence. If it is necessary to pack the evidence separately, a copy of the letter should be placed in every package so that the recipient will know immediately the import of the contents. All items of evidence should be marked and described exactly in the accompanying letter so that they will not be confused with packing material of a similar nature, and to provide a check on what the package should contain.

In addition, the letter should include for record purposes a brief outline of the crime, i.e., type, date and place of occurrence, and names of victims and subjects. If suspects are named for comparison, sufficient descriptive data should be set out to permit location of their fingerprint records. This information, in preferential order, comprises the individual's complete name, aliases, FBI number, date of prior arrest or fingerprinting, fingerprint classification, date and place of birth, and physical description.