If a fingerprint is visible, an effort should be made to photograph it before any attempt is made to develop it. In every case a print developed with powder should be photographed before lifting. It sometimes happens that the print does not lift properly although it may be quite clear after development.
The camera which is especially adapted to the purpose and which is easiest to handle and operate is the fingerprint camera, one type of which is shown in figure 424. This camera has several advantages in photographing fingerprints:
It photographs the prints in natural size.It contains its own light source.It has a fixed focus.
It photographs the prints in natural size.It contains its own light source.It has a fixed focus.
Fig. 424
[Fig. 424]
Cameras of this type are available in models operated by batteries and 110-volt current. It is believed that the battery-operated type has the greater utility, since house current may not be available at the crime scene. When not in use the batteries should be removed as they will eventually deteriorate and corrode the brass contacts in the camera.
The camera is of the box type and has three button controls which will open: (1) The metal flap covering the aperture, (2) the front portion of the frame providing access to the self-contained light bulbs, and (3) the camera in half, providing access to the batteries and the shutter as shown below in figure 425.
Fig. 425
[Fig. 425]
A 2-1/4 x 3-1/4 film pack adapter or a 2-1/4 x 3-1/4 cut film holder holds the film in the camera. The film pack adapter will hold a pack of 12 sheets of film, and accordingly, will permit the taking of 12 pictures. The cut film holder is a unit which holds two sheets of film utilizing each side of the holder.
It is pointed out that the FBI uses the film pack exclusively in view of the fact that practically all latent examinations will necessitate the taking of more than two pictures. Further, the film pack is made so that it may be loaded into the adapter in the open light. Also, the films are numbered 1 through 12, which is a valuable feature in that in maintaining notes concerning the latent examinations it is a simple matter to note by the number of the negative where the latent impression was developed and photographed. Should it happen that during a latent examination all twelve of the films are not used, the film pack, with the slide in place, is taken into the darkroom and only those films which have been exposed are removed and developed. The unexposed films remain in the film pack adapter with the slide in and may be used later.
As was previously mentioned, the camera has a fixed focus; that is, the camera will take a legible picture only when the latent print is at the focal point, or exactly flush with the opening of the camera. The latent print must not be inside the open end of the camera, nor must it be beyond; otherwise, the picture will be blurred.
Since the camera has its own light source, any leakage of outside light will cause overexposure of the film. Consequently, if the surface of the object bearing the latent print which is to be photographed is uneven or does not cover the entire front of the camera opening, it will be necessary to use some opaque material such as a focusing cloth or heavy dark material to cover the front of the camera so as to exclude all outside light (fig. 426). If a latent print on a pane of glass or an automobile window is being photographed, it will be necessary to back up the latent so that there will be no light leakage. Material showing a pattern or grain should not be used for this purpose as any such pattern will photograph in the background and possibly obliterate the ridges of the latent print.
Fig. 426
[Fig. 426]
To insure an equal distribution of the light over the latents being photographed, the impressions should be centered in the opening of the camera. This is accomplished by opening the angular front section of the camera after the metal plate covering the front has been opened, and setting the aperture over the latent impressions so that they will be as near the center as possible. Then, holding the camera firmly in place, it is carefully closed (fig. 427).
Fig. 427
[Fig. 427]
During exposure the camera must be held perfectly still. Any movement of the camera or object will result in a fuzzy or double image.
In photographing a small, movable object such as a bottle or tumbler, the camera should not be placed on its end and an attempt made to balancethe object across the opening. Instead, the camera should be placed on its side and the bottle or tumbler built up to the opening so that there is no necessity for holding the object (fig. 428). There will be, of course, instances where the camera will have to be held, such as to the side of a wall, cabinet or automobile. Here an extreme effort should be made to avoid moving the camera or permitting it to slip during exposure.
Fig. 428
[Fig. 428]
Anticipating the possible use of the photographic negatives in a court proceeding, it becomes of paramount importance to be able to identify them. This is done by using what is called an identification tag. The tag consists of a small piece of paper bearing the date, initials of the examiner, and possibly a case number, and it should be hand-written. The tag is placed near the latent prints being photographed so that it will appear in the picture. It should be borne in mind that concentration should be on the latent impressions, which must be centered, and the identification tag should be to one side and not covering any of the latent prints. Another method of identification, if the surface permits, is to write the above-mentioned data on the surface of the object bearing the latents so that the information set out will also be a part of the picture. Too much emphasis cannot be placed on the importance of the identification tag.The lack of such data, by discretion of the court, may exclude the latents as evidence, in the absence of the original specimen bearing the latents.
The following are suggested exposure times for Tri-X film (available in 2-1/4" x 3-1/4" film packs) with battery-operated cameras having lenses without diaphragms:
Black powder print on white or light background—snapshotGray or white powder print on black or dark background—1 second
Black powder print on white or light background—snapshotGray or white powder print on black or dark background—1 second
These same exposure times can be used on some cameras having lenses with diaphragms, provided the lens opening is set at f6.3.
The above exposure times are for cameras with batteries in average condition. If batteries become weak the exposures may be increased slightly.
In making snapshots the shutter mechanism should be manipulated as rapidly as possible since slow motion will appreciably lengthen the exposure. In making time exposures the camera shutter must be held open for the desired time. Personnel with photographic experience may desire to use cut film with the fingerprint camera. A few tests will determine the optimum exposure times for any particular type of film.
Briefly, the procedure for taking photographs of latents is as follows: The film pack is placed into the film pack adapter with the safety paper side of the film pack to the slide side of the adapter, care being taken to see that all of the paper tabs are outside of the adapter. The adapter is placed on the camera in its proper position by opening a slide clamp attached to the camera, fitting the side of the adapter into the slot away from the clamp and pushing it down flat into the opening. Don't try to slide the adapter into the opening from the top. The adapter is locked in position by closing the clamp. Next the slide is removed and the tab marked "Safety Cover" pulled out as far as it will come and torn off. The camera is placed in position and the first exposure made; then thetab marked "1" is pulled and the next film is in position for exposure. This procedure is followed with each succeeding film until all have been exposed.
When the last tab has been pulled out, the pack can be removed from the adapter in daylight. If all of the films have not been exposed the slide is replaced into the adapter and the film pack removed from it in a darkroom, as previously stated.
As a matter of regular policy, it is recommended that more than one exposure be made of each latent, varying the normal exposure time to insure satisfactory results, especially when the contrast is not a good black on white or gray on black.
Before starting to photograph, note the following:
● Check shutter action.● Check bulbs, batteries, and lights.● Center latents in opening of camera.● Latent being photographed must be flush with opening of camera.● Outside light must be excluded.● Include identification tag in photograph.● Remove slide and pull safety tab of film pack before making exposure.● Hold camera still while making exposure.● Pull correct number tab after each exposure (be careful not to pull more than one).● Do not use grained or uneven material as a backing when photographing latents on transparent glass.● Mirrors, polished chrome, and nickel plate will photograph black in the fingerprint camera.
● Check shutter action.
● Check bulbs, batteries, and lights.
● Center latents in opening of camera.
● Latent being photographed must be flush with opening of camera.
● Outside light must be excluded.
● Include identification tag in photograph.
● Remove slide and pull safety tab of film pack before making exposure.
● Hold camera still while making exposure.
● Pull correct number tab after each exposure (be careful not to pull more than one).
● Do not use grained or uneven material as a backing when photographing latents on transparent glass.
● Mirrors, polished chrome, and nickel plate will photograph black in the fingerprint camera.
The foregoing has dealt with the standard use of the fingerprint camera when the direct light afforded by the camera gives suitable results. There will be cases, however, where the results from the use of the direct light may not be adequate. Such cases may involve molded or embedded prints, such as prints in putty, wax, soap, etc. Should direct light give poor results, side lighting may prove effective. This can be done by loosening two of the bulbs on one side so that they will not light. The light given by the other two bulbs is directed so as to pass at right angles, as much as possible, across the ridges of the embedded latent print. Adjustment of the exposure time must be made when this is done.
In testifying to fingerprint identification, the expert often prepares charts to visually aid the court and jury in understanding the nature of his testimony. Many times it is undoubtedly difficult for the layman to perceive, from a vocal explanation alone, the full import of an expert's testimony, due to its technical nature; consequently, some graphic representation of the facts presented is amply justified and rewarded. The preparation of the charts is ultimately the sole responsibility of the expert using them. As a matter of interest to law enforcement personnel engaged in fingerprint work, a brief explanation of the preparation of such charts follows, along with suggestions and remarks based on long experience in these matters.
To do the work conveniently, it will be necessary to have available, in addition to the ordinary photographic developing and printing materials, a projection enlarger which will enlarge preferably to at least ten diameters. In the projection method of enlargement, the image is printed directly from the original negative, and the preparation of an enlarged negative is unnecessary.
Aside from the photographic equipment, the needed materials are: a roll of scotch photographic tape 1 inch wide to outline the areas of the fingerprints on the negatives to be used; some stiff cardboard approximately 1/32 inch thick on which to mount the prepared charts; a tube of rubber cement; and a bottle of translucent ink, other than black or white.
A light-box on which to view the negatives while blocking, and a lettering set to draw the lines and numbers uniformly on the charts, while not absolutely essential, are helpful conveniences. A light-box is basically a frosted pane of glass with a light beneath it to produce soft, even, non-glaring illumination. If no light-box is available, a clear window may be utilized in "blocking" the negatives.
If the expert finds it necessary to have an outside source prepare his photographs, he should retain personal custody of the evidence during the operation.
The original latent print and inked print with which it is identical should be photographed actual size. This procedure eliminates guesswork in enlarging both to the same degree. Whatever areas of the two prints are deemed requisite to illustrate the method of identification are then outlined (blocked) on the negatives with the masking tape, so that only those areas will show in the subsequent enlargements. Generally, if thelegible area of the latent print is small, it is well to show the complete print. If the area is large, however, as in a palm print, an area which will not make the chart too bulky or unwieldy may be selected.
In blocking, the negative is affixed to the window pane or light-box by means of strips of photographic tape across the corners, with the side to be blocked up. This prevents constant shifting of the negative while it is being prepared. The latent print should be blocked first. Corners of the blocked areas should be square. Care should be exercised to have as nearly as possible the same ridge formations shown and the ridge formations in the same upright or horizontal positions. This may be facilitated by fixing a negative, bearing ruled squares, between the negative being blocked and the glass to which it is attached.
If the latent print was developed or photographed as a light print on a dark background, a reverse-color negative should be prepared and blocked in order that both prints may appear as black ridges on light backgrounds. This is done by placing the original negative adjacent to a new sheet of film and exposing it. The resultant negative contains the same image as the original except that the color of the image has been reversed.
If the negative is a photograph of an opaque lift, the print appears in reverse position; that is, as a mirror image, and the negative will accordingly have to be blocked from the dull or emulsion side in order for it to appear in a position comparable to that of the inked print.
Failure to present the prints in question in the same color and position may possibly confuse the observer and nullify the purpose for which the chart is made.
The degree of enlargement is not important in itself, so long as the ridges of the latent print are readily distinguishable by the eye. Ten diameters have been found adequate, although any enlargement from 5 to 30 will serve. It should be remembered, however, that small enlargements are difficult to see a few feet away and that large ones lose some of the contrast between ridges and background. A white border of at least 1-1/2 inches or a width equal to about one-third the enlarged area should be left for charting purposes.
Any chart prepared must be technically correct; that is, the corresponding ridge characteristics in the two prints must be similarly numbered and indicated.
Several ways of pointing out the similar ridge formations have been observed, but the one which appears soundest is also simplest and consists of merely marking the characteristics with lines and numbers.
All of the ridge characteristics in the prints need not be charted. Twelve characteristics are ample to illustrate an identification, but it is neither claimed nor implied that this number is required.
All fingerprint identifications are made by observing that two impressions have ridge characteristics of similar shapes which occupy the same relative positions in the patterns.
Methods involving superimposition of the prints are not recommended because such a procedure is possible only in a very few instances, due to the distortion of ridges in most prints through pressure and twisting. Such a procedure is not necessarily a test of identity.
Likewise, presenting charts with the shapes of the characteristics drawn in the margin is not recommended. Individual ridge characteristics may vary slightly in actual shape or physical position due to twisting, pressure, incomplete inking, condition of latent print when developed, powder adhering to background, etc. Identifications are based on a number of characteristics viewed in a unit relationship and not on the microscopic appearances of single characteristics.
Since the enlarged photographs appear in black and white, an ink other than black or white should be used to line the chart. Such an ink should be preferably translucent so that it will be possible to see the ridges which it traverses. A translucent carmine drawing ink serves well. In placing the lines on the chart, they should be arranged so that they do not cross or touch.
The chart will present a clearer, neater, and more pleasing appearance if it is numbered clockwise and the numbers are evenly spaced (fig. 429). It is not necessary, however, to place the numbers evenly around the photograph.
Fig. 429
[Fig. 429]
Ordinarily, the numbers are placed on three sides and the type of print (latent or ink) noted at the bottom. In any case, the manner of numbering should be subservient to an explanation of the characteristics in an orderly sequence; and, if the situation warrants it, all of the points may be illustrated on a single side of the photograph.
A single line should be drawn from each characteristic to a numbered point on the margin. Care should be taken to draw the line exactly to the characteristic point, not short of it, beyond it, or obscuring it. Erasures should be avoided. If the ink runs or blots, it is sometimes possible to remove it with a cloth dampened in denatured alcohol, without damaging the photograph.
If the enlargement is great, that is, 25 or 30 diameters, it might be well to draw a small circle around each characteristic and then draw the line from the circle to the number, since the ridge will be much thicker than the illustrating line. All lines and numbers should be checked for absolute accuracy. The expert should also study the enlargements forapparent discrepanciesin the prints, which he might be called upon to explain.
The charted enlargements are readily mounted on stiff cardboard with rubber cement, which may be purchased in small tubes. After cementing the photograph to the cardboard, it should be placed under a heavy flat object which will cover the entire surface until dry to prevent warping and wrinkling. After drying, trim the two enlargements to the same square size with heavy scissors, a pen knife or scalpel, and fasten them together, book-fashion, with strips of the photographic tape used in blocking the negatives. Of course, if charts are large, 20 to 36 inches square, mounting is unnecessary and they will have to be supported in the courtroom with thumbtacks or metal rings.
Some courts do not permit numbering or lining of the photographs and the enlargements alone in these cases will have to suffice. If there is some question about admissibility of the charted enlargements, it is well to prepare an extra uncharted set.
From time to time the FBI is requested to conduct surveys and participate in conferences and in police schools on the problem of fingerprint identification.
As a result of its observations in the course of these activities it has been found that many identification bureaus are not fully aware of the importance which latent finger impressions can have in connection with the ordinary handling of arrest fingerprint cards.
Many bureaus and departments spend considerable time in developing latent impressions in a particular case. If no immediate results are forthcoming, the latent impressions are filed for future reference.
Single fingerprint files have been maintained with success by some departments. Many others do not attempt to keep a file because of either limited personnel or lack of funds. In many departments, however, where such a file is maintained, too often latent impressions are simply filed with no regard to possible future use. Actually, these impressions should be treated as evidence directly connecting the subject with the crime.
Active consideration should be given to the latent impressions until they are identified or the case has been successfully prosecuted. It is definitely felt that the following suggested procedure might have some decided advantages.
It is suggested that in all cases where latent impressions are developed at the crime scene, or on an object used in connection with the commission of a crime, the impressions be properly photographed and lifted. The evidence, where possible and practicable, should be properly packed, labeled, and stored for future use in court (fig. 430).
Fig. 430
[Fig. 430]
Use care in wrapping the evidence to see that the latent impressions on the objects are not destroyed. If the specimens are later used in court, the impressions should still be clearly visible. In the same manner, all evidence not of a bulky nature, such as photographic negatives, photographs, and lifts of latent impressions, should be similarly preserved for future court use. It is to be emphasized that all material in one case should bear a case number. All specimens not of a bulky nature can be placed in an envelope and filed by this case number (fig. 431).
Fig. 431
[Fig. 431]
The above procedure is the usual one followed by the majority of identification bureaus in handling latent impressions. In order, however, to keep the latents in an active state, the photographs of all the latent impressions found in a particular case should be cut up and pasted on a 3 by 5 card bearing the case number and title of the case (fig. 432).
Fig. 432
[Fig. 432]
If numerous latents are developed, several cards should be used, allhaving the same number and title. These cards are then filed by case number in a regular filing cabinet. Before this step is taken, every effort should be made to secure and compare the fingerprints of individuals who may legitimately have placed their prints on the objects which were examined. In addition, as part of the case report bearing the same case number as the latent impressions, there should be a notation pointing out that latent impressions were developed in the case and that they are on file.
Fingerprint comparisons in this unidentified file can be made on the basis of fingerprints taken from day to day of individuals fingerprinted for criminal identification purposes. A routine may be set up whereby the fingerprints of individuals arrested each day will be compared the following day with the latent fingerprints filed in the unidentified latent file. It is most important that this procedure be rigidly followed from day to day. It is to be borne in mind that the comparisons are made whether the particular person is or is not a suspect in a certain case. Special attention should be paid to fingerprints of individuals charged with burglary, breaking and entering, armed robbery, and other similar crimes.
Should an identification be made of some latent prints, and others in the same case remain unidentified, the 3 by 5 card should remain in file until the case is fully closed, inasmuch as more than one person may be involved in the crime. Of course, if all the latents are identified, then the 3 by 5 card is removed and placed with the negatives, lifts, etc.
It may be deemed advisable to remove these latents from the file in instances where the statute of limitations covering the crime has run.
If the above procedure is rigidly followed, identification in many instances will result—more than would be effected if the department maintained only a single fingerprint file in which the latent prints were merely filed away. Very often such a latent fingerprint file is a source of information when all logical investigative leads have been exhausted.
This résumé of latent impressions has been prepared by the Federal Bureau of Investigation in the belief that it may be of possible interest to law enforcement officers desiring to avail themselves of latent identification evidence in connection with their investigative activities. It should be borne in mind that the comments and expressions set out in this book are not intended to convey the thought that the Federal Bureau of Investigation believes the points emphasized are the only ones of moment, or that other methods of developing latent impressions are not equally acceptable. The Federal Bureau of Investigation will be glad to answer any questions on the foregoing which may occur to any law enforcement officer who reads this material.
This résumé of latent impressions has been prepared by the Federal Bureau of Investigation in the belief that it may be of possible interest to law enforcement officers desiring to avail themselves of latent identification evidence in connection with their investigative activities. It should be borne in mind that the comments and expressions set out in this book are not intended to convey the thought that the Federal Bureau of Investigation believes the points emphasized are the only ones of moment, or that other methods of developing latent impressions are not equally acceptable. The Federal Bureau of Investigation will be glad to answer any questions on the foregoing which may occur to any law enforcement officer who reads this material.