Latent Impressions

Each ridge of the fingers, palms, and soles bears a row of sweat pores

which in the average person constantly exude perspiration. Also, the

ridges of the fingers and palms are in intermittent contact with other

parts of the body, such as the hair and face, and with various

objects, which may leave a film of grease or moisture on the ridges.

In touching an object, the film of moisture and/or grease may be

transferred to the object, thus leaving an outline of the ridges of

the fingers or palm thereon. This print is called a latent impression,

the word latent meaning hidden, that is, the print many times is not

readily visible.



Latent impressions, regardless of the area of the ridges present, are

of the greatest importance to the criminal investigator as

identification of them may solve the crime and result in successful

prosecution of the subject. Consequently, every effort should be made

to preserve and identify them.



Visible prints in mediums such as blood, grease, dirt, or dust are

equally important to the investigator but, strictly speaking, are not

latent impressions.



A search of the crime scene should be conducted in a logical manner.

Points of entry and exit should be examined, along with surfaces or

objects disturbed or likely touched during the commission of the

crime. The examiner should wear a pair of light cloth gloves and

handle an object only insofar as is necessary and then only by edges

or surfaces which are not receptive to latent impressions. A record of

the exact location of a print on an object and of the object itself

should be made, since these facts may be of the utmost importance in

any trial resulting from the investigation. No one should handle an

object other than the examiner himself.



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.



Evidence is preferably forwarded by registered mail or railway

express, as these means provide records of dispatch and receipt.



Elimination or suspect fingerprints are best enclosed with the

evidence itself, with a notation as to the type of prints forwarded.