The Science of Fingerprints by United States. Federal Bureau of Investigation (books to read in a lifetime txt) 📕

finger and this number is used as the final. It will also be noted that there is a loop of 24 ridge counts in the right thumb and this number is used as the key inasmuch as it is the first loop. In this example, the print is searched in the group classification which has finals ranging from 15 through 19. Within this group of finals the prints which have keys ranging from 22 through 26 are examined. Referencing

Too much stress cannot be placed upon the necessity of referencing questionable patterns, whether it be in the interpretation of the type of pattern, the ridge count, or the tracing.

The factors which make it necessary are: variation in individual judgment and eyesight, the amount of ink used, the amount of pressure used in taking the prints, the difference in width of the rolled impressions, skin diseases, worn ridges due to age or occupations, temporary and permanent scars, bandaged fingers, crippled hands, and amputation.

For the highest degree of accuracy, all rolled impressions should be checked by the plain impressions, which generally are not distorted by pressure. This also helps prevent error caused by the reversal or mixing of the rolled impressions out of their proper order. For the same reason, as much of the counting and tracing should be done in the plain impressions as it is possible to do.

If there is any doubt as to which of two or more classifications should be assigned to a given pattern, it is given the preferred classification and reference searches are conducted in all other possible classifications. For example, if on a print with the preferred classification

1 A 1 Aa

it is questionable whether the left middle finger should be a plain arch, a tented arch, or a radial loop, the print is searched in the

1 A 1 Aa

group, and reference searches are conducted in the

1 A 1 At

and

1 A 1 Ar

groups. For further illustration, a print is given a preferred primary classification of

1, 1

although the ridge detail on the right thumb is so formed as to resemble a whorl. The search is completed first in the preferred

1 1

primary classification and a reference search is then conducted in the

1 17

primary.

All ridge counts that are "line counts," i.e., when one more or one less count would change the designation of the loop from I to O or from S to M, etc., must be searched in both groups. For example, in a print classified

16 M 1 U III 10, M 1 U III

if the ridge count of the right middle finger is 10 and the count in the right thumb is 16 (as indicated by the key), the print would be searched first as classified, then reference searches would be conducted in the following groups:

M 1 U IOI,   L 1 U III, and L 1 U IOI M 1 U III M 1 U III M 1 U III

When there is doubt concerning the tracing of a whorl, it should be treated in the same fashion. For example, if in the classification

O 5 U I 17 U

doubt existed as to whether the tracing of the right thumb might not be a meeting tracing, the print would be searched as classified, and a reference search would be conducted in

M 5 U. I 17 U

If there is no doubt concerning the ridge count used for the final, it is enough to search out of the group only those prints containing a final within 2 ridge counts on each side of the final on the print being searched. When, however, there is doubt concerning the ridge count of the final, the print should be searched 2 ridge counts on each side of the two extremes of possibility. For example, if it were possible for a final to be 6, 7, 8, or 9 ridge counts, the print should be searched through that part of the group bearing finals of from 4 through 11.

The above explanation pertaining to the final also applies to the key.

All prints bearing amputations should be referenced to the necessary files containing prints other than amputations for reference searches.

In instances where only one finger is amputated, reference searches are conducted in all possible classifications, including all possible ridge counts or tracings. For example, a print containing the classification:

AMP
  4 S 1 U III 6 S 1 U III

with the right index finger amputated, the left index finger being an ulnar loop, would be searched first in the amputation group for the classification, then reference searches would be conducted in the following groups in the nonamputation files:

S 1 U III   S 1 T II   S 17 W III S 1 U III S 1 U III S 1 U III

 

S 1 U OII   S 1 R III   S 17 W MII S 1 U III S 1 U III S 1 U III

 

S 1 A II   S 1 R OII   S 17 W OII S 1 U III S 1 U III S 1 U III

 All prints bearing unprinted or badly crippled fingers are filed in the nonamputation files, and reference searches are conducted in the amputation group.

For the purpose of determining if it is feasible to conduct reference searches in all possible classifications, the method of referencing amputations is applied to completely scarred patterns (Chapter titled "Scarred Patterns—Amputations—Missing at Birth"). For example, a print bearing the preferred classification:

13 O 17 W OOO 14 L 17 U OOI

with the left middle finger completely scarred, the right middle finger being an ulnar loop with a ridge count of 13, would be searched first in the group for that classification, then reference searches would be conducted in the following groups:

O 17 W OOO   O 17 W   O 19 W OOO L 17 U OII L 17 Ur L 17 U OOI

 

O 17 W   O 19 W OOO L 17 Ua L 17 U OII

 

O 17 W   O 19 W OOO L 17 Ut L 17 U OMI

The referencing of partial scars is a problem in which many factors are present. A full explanation of the scars, their preferred classifications and their references is made in the chapter, "Classification of Scarred Patterns—Amputations—Missing at Birth."

When the age extension is utilized and a "Reference" group and a "Presumptive Dead" file are maintained, it is suggested that a general allowance of 5 years be considered to allow for a discrepancy in prints bearing the ages of 50 years or older.

In the files of the Federal Bureau of Investigation the various age groups are as follows:

1-54 "Regular" file. 55-74 "Reference" file. 75 and over "Presumptive Dead" file.

Reference searches for the preceding groups are conducted in the following manner:

50-54 Referenced to "Reference" file. 70-74 Referenced to "Presumptive Dead" file and "Regular" file. 75-79 Referenced to "Reference" file and "Regular" file. 80 and older Referenced to "Regular" file only.

If no age is given, it should be searched first in the regular file and reference searches should be conducted in the "Reference" group and the "Presumptive Dead" file.

When separate male and female files are maintained, there may be doubt as to the sex of a subject due to a discrepancy between the sex indicated and the name and the description and picture. In such case try to determine the sex from the description and the size of the prints, then reference the print to the other file. A Photostat copy can be made and placed in the other file until the true sex can be determined.

CHAPTER VIII How To Take Inked Fingerprints

 

The equipment required for taking fingerprints consists of an inking plate, a cardholder, printer's ink (heavy black paste), and a roller. This equipment is simple and inexpensive.

In order to obtain clear, distinct fingerprints, it is necessary to spread the printer's ink in a thin even coating on a small inking plate. A roller similar to that used by printers in making galley proofs is best adapted for use as a spreader. Its size is a matter determined by individual needs and preferences; however, a roller approximately 6 inches long and 2 inches in diameter has been found to be very satisfactory. These rollers may be obtained from a fingerprint supply company or a printing supply house.

An inking plate may be made from a hard, rigid, scratch-resistant metal plate 6 inches wide by 14 inches long or by inlaying a block of wood with a piece of glass one-fourth of an inch thick, 6 inches wide, and 14 inches long. The glass plate by itself would be suitable, but it should be fixed to a base in order to prevent breakage. The inking surface should be elevated to a sufficient height to allow the subject's forearm to assume a horizontal position when the fingers are being inked. For example, the inking plate may be placed on the edge of a counter or a table of counter height. In such a position, the operator has greater assurance of avoiding accidental strain or pressure on the fingers and should be able to procure more uniform impressions. The inking plate should also be placed so that the subject's fingers which are not being printed can be made to "swing" off the table to prevent their interfering with the inking process. A fingerprint stand such as that shown in figure 360 may be purchased from fingerprint supply companies. The stand is made of hardwood and measures approximately 2 feet in length, 1 foot in height and width. This stand contains a cardholder and a chrome strip which is used as the inking plate. Two compartments used to store blank fingerprint cards and supplies complete the stand. This equipment should be supplemented by a cleansing fluid and necessary cloths so that the subject's fingers may be cleaned before rolling and the inking plate cleaned after using. Denatured alcohol and commercially available cleaning fluids are suitable for this purpose.

 

Fig. 360

[Fig. 360]

 

The fingerprints should be taken on 8- by 8-inch cardstock, as this size has generally been adopted by law enforcement because of facility in filing and desirability of uniformity. Figure 361 shows fingerprints properly taken on one of the standard personnel identification cards from the Federal Bureau of Investigation. From this illustration, it is evident there are two types of impressions involved in the process of taking fingerprints. The upper 10 prints are taken individually—thumb, index, middle, ring, and little fingers of each hand in the order named. These are called "rolled" impressions, the fingers being rolled from side to side in order to obtain all available ridge detail. The smaller impressions at the bottom of the card are taken by simultaneously printing all of the fingers of each hand and then the thumb without rolling. These are called "plain" or "fixed" impressions and are used as a check upon the sequence and accuracy of the rolled impressions. Rolled impressions must be taken carefully in order to insure that an accurate fingerprint classification can be obtained by examination of the various patterns. It is also necessary that each focal point (cores and all deltas) be clearly printed in order that accurate ridge counts and tracings may be obtained.

 

Fig. 361

[Fig. 361]

[Enlarge]

 

In preparing to take a set of fingerprints, a small daub of ink should be