Fingerprint Photographic Technique for Recover of Marks - Research Paper Example

Fingerprint Photographic Technique for Recover of Marks Fingerprint Photographic Technique for Recover of Marks Introduction Forensic scientists and crime experts have extensively used fingerprints in criminal investigations in determination who are the perpetrators, victims and witnesses besides their differentiation (Houck and Siegel, 2010, p. 1). Fingerprints are used because they have two advantages mainly uniqueness and persistence. Persistence arises from the fact that they do not to change with time only permanent scarring can change them (Houck and Siegel, 2010, p. 3). Their uniqueness arises in that fingerprints are so different in that even in identical twins have varying fingerprints patterns. In general we have three types of fingerprints mainly latent, plastic and patent prints. Latent prints are formed from oils and sweat from the skin surface. They are invisible to un-aided eye, therefore; they require additional treatments. Patent fingerprints are made from ink, grease, dirt and blood. They are visible to the naked eye. Finally, the plastic fingerprints are in three-dimension, and they are made after pressing the hands on fresh soap, wax or paints. The prints are visible to the naked eye (Houck and Siegel, 2010, p. 29). To improve the visibility of latent fingerprints various lighting techniques can be used to obtain the invisible surfaces. According to Chaikovsky, Argaman, Batman, Sin-David, Barzovski and Yaalon (2005, p. 574), digital multiple exposure technique is applied. The process is simple and productive. Digital photography and computerized image processing with application of layers methodology produce many images that are easily controlled by computer programmes. Production of many images that are combined into a single image enables improved visualization of the selected portions of the latent print without affecting the rest part of the image. According to SIRCHIE (2013, p. 1), Crime scene photos are important in the crime scene inquiry. The photographs complement the investigator data in the form of data. A camera can be used to capture every object of importance within the crime scene. Warren (2014, p. 1), conducted a research to determine usage digital photography for forensic purposes. It was found out that digital imaging devices with spectral filters are very effective in the identification of untreated latent fingerprints in that it is viable and non destructive. According to the National Law Enforcement (2011, p. 6), it is believed that every individual has different body parts hence comparison of the measurements can be used to distinguish between two individuals. The method was developed by Alphonse Bertillon. He was a French criminologist who came up with the idea of anthropometric systems of physical measurements. The measurements involved the head and face which on the combination produced a detailed description of the person. However, their method got some controversies in 1903 when a suspect by the name Will West was photographed using the system. The measurements were identical to a criminal by the name William West who had been sentenced. The investigators were not aware that the two men were related. Therefore, to avoid such confusions, the Bertillon system was abandoned, and the fingerprinting method adopted to avoid such confusions. According to Dowdey (2012, p. 1) forensic photographs are crucial in crime investigations. Owing that most data is transitory, in that on lifting of fingerprints, bodies are taken away, and the crime scene completely changed. For example if it is in the home, the tables and chairs among the furniture presents at the crime scene will be re-arranged. Blood stains will be cleaned away, and there will be no evidence left for future reference to elaborate how the crime scene looked during the incident. Therefore, photographing can provide very vital information after the crime is gone. Keywords Camera: Resolution, Depth of Field, Circles of Confusion, Perspective Error, PPI, macro lenses, Jpeg/Raw. Lighting: Inverse Square Law, Cosine Law. Camera A camera is an electronic, optic device that records images that are stored, transmitted to another location or both (Horn, 2009, p. 2). The images may be in the form of static photographs or moving images such as videos and movies. The recorded image is recorded in the electronic sensor or the photographic film. The camera lens captures the light from the objects and brings it into a finer focus on the film or detector. Lenses are made of a wide range of focal lengths. Every lens is suited to a particular photo. Only objects that are close to the camera lens are produced clearly. Therefore, for distanced images camera focus should be changed. Oblique lighting with the ALS Photographing of footwear impression in the dust sometimes becomes difficult especially if the dust print was isolated from highly reflective surface such as a gelatin lift. According to Baldwin (2014, p. 1), reflective surfaces will always cause some glaring back to the camera. To solve the issue, ALS is applied in that a beam of light can be positioned such that the light is in parallel with the reflective surface. Not only should the process be applied in footwears patterns, but also finger and palm printing to show any disturbance or no disturbance of the evidence at the crime scene. The exposure time is approximated to be about 12 seconds. The light source and the object distance influences the exposure time. It should be noted that the white frequencies of the ALS should be used for less than 45 seconds in that they may burn the optic fibre cord if the duration is beyond. Luckily, there is no harm that may arise if a liquid fibre optic cord is used (Baldwin, 2014, p. 1). There are three main methods of making the invisible latent fingerprints visible (Houck and Siegel, 2010, p. 11). They are mainly physical, chemical and instrumental techniques. Super glue process also known as cyanocycrate fuming process is under the chemical method. Brown deepens further by claiming that latent fingerprints are composed of several chemicals that are produced from the body pores, and they are virtually left on any object touched. The main components of latent fingerprints are sweat, solids and organic compounds such as amino acids, lactic acids, riboflavin, glucose and iso-agglutinogens besides inorganic compounds such as potassium, sodium and chlorine among others. Sweat is mainly water and will, therefore, evaporate within a very short time. The basic concept behind all the chemical techniques is to apply a substance that will produce a visible fingerprint after a chemical reaction occurring between the applied chemical and the present compound. Therefore, presence of the visibility enables photographing of the images (Houck and Siegel, 2010, p. 11). Photography Photography is a field that deals with creating images after recording light and electromagnetic radiations by chemical use of light sensitive materials such as photographic films or electronically by use of image sensors. The method applies development of fingerprints from latex gloves using standard techniques for macro photography. A copy stand is always used with the photos being taken with a scale of 1:1. Light sources, goggles and special filter are used to visualize the fluorescent evidence. All ALS/LASER enhanced photos are negative images with the fluorescent dyes and powders being white in a black background. The photographs are reversed in darkrooms for easier comparison using the latent print examiner. According to Smith (2008, p. 1), the irregular shape of the latex gloves makes it hard for comparison. Therefore, special care should be taken for usable results to be attained. Several experiments were run in determination of the best method. The gloves were put between two glass panes but the problem worsened in that confusing folds and ceases were produced. Moreover, the glass contact on the powder caused smearing that led to the loss of some details. Fine and good results were obtained by cutting the gloves apart and spreading the finger into a flat mode. On the contrary, the gloves were destroyed leading to loss. The best results were obtained when the scraps of transparent material were cut with the shape of fingers. The plastic fingers were inserted into the gloves and flattening could be accomplished without distortion and photographing done (Smith, 2008, p. 1). Field Of View Field of view (FOV) is the size of the observable area that is captured by the camera at a particular lens. Whenever the FOV is not suitable, it is always advisable to use different lenses in a way of increasing or reducing the FOV. Camera lenses can be classified as either focal or varifocal. A fixed focal lens has a fixed focal length always while varifocal lens can vary its focal length. In a precise manner, focal length is the distance between the optical centre and a point at the end of the lens back. The distance is calibrated on the lens, and it is always in millimetres as its unit. Fixed focal length lenses are wide, medium or narrow field of view. A standard focal length lens produces a picture that is always in an approximate range of view similar to the human eye. A wide-angled lens has a short focal length. On the other hand, telephoto lens has a long focal length. Therefore, whenever a detective wants to change the field of view, the lens should be changed too (APTA. 2011, p. 11). F-stop Aperture is the opening power of the lens. The ability of any lens to collect and gather light depends on the focal length and the lens opening creating the f-stop. Therefore, f-stop is the ratio between the lens aperture and focal length. For example, a lens with a 15mm focal length with 3mm aperture will give an f-stop of 5. The low the number of the f-stop, the larger the maximum lens aperture hence the powerful is the lens ability to pass light into the camera imager, therefore, the better low-light scenes are seen better. Sometimes a lens with a small f-stop is termed as a faster lens (APTA. 2011, p. 11). Depth of Field (DOF) Whenever determining the best lens, one should always consider the depth of field. DOF is the range distance within a sharply visible image. Sometimes when taking a photo, the distance before and after the object is taken therefore, covering unnecessary regions of the photo. DOF will always depend on the lens focal length, distance of the camera to the object and the camera aperture. Combination of the three factors created a very sensible relationship as follows. Short lens have a long depth of field and vice versa. Wide aperture will always produce shorter depth of fields and vice versa. Finally short distance from the object to the camera will create shorter depth of fields (APTA. 2011, p. 12). Camera features such as F-stop, lenses and distance between the subject and the camera affects depth of field so much (Robinson, 2010, p. 157). To increase the DOF, it is advisable for the photographer to use the hyper focal; focus. Moreover, 5ghe rule of thirds can be applied in large crime scenes when there is no infinity at the background. On bright days, photographs with small f-stops are observed using the ISO 200 film. In contrast, ISO 400 worked best on dark or cloudy times when visibility is poor due to lighting (Robinson, 2010, p. 166). A wise photographer should dial the speed of the film into the camera, position the shutter speed at an average a-sixtieth of a second with the f-stop at 8. Ion taking the meter reading, the value should have the estimated exposure and over-exposure for its validity approval. One can then load it into the camera for image taking. In a fully lit area, some region before and after the object will be seen provided that the f-stop is high. Therefore, it is now evident that the depth of field and lighting conditions should always be considered whenever selecting cameras and lenses. Ina r4as whereby the objects present at the scene of the crime are critical; it is always important to operate in very low light beside provision of supplementary sources of light (APTA. 2011, p. 11). Selection of Lenses Selection of lenses will always be dictated by the view to be covered and the cameras optical format. However, the sensor and the optical format must be matched. For all cameras to be placed to record images at the point of transaction such as parking garages, the interest of the investigator will be the number plates of the cars. Moreover, the colour and model of the cars will be significant but in this case, the number plates will help much. Therefore for such objects, the number plate should cover approximately more than 15% of the cameras field of view. In the case of human beings, the average human head is approximated to be six inches wide. Therefore, a three feet field of view will be very efficient. Similarly, a 12 inch long number plate will require a minimal field view of six feet. All cameras monitoring interior and exterior regions should have all their focal lengths selected for them to capture and ensure that the walking pace of the objects is within the focus (APTA. 2011, p. 11). Resolution of a Camera Camera resolution is its ability to see small details in the image. It is a monochrome specification that determines how many black and white lines can be observed in a particular area. It is specified in terms of horizontal resolution lines. In general high resolution cameras cost more than lower ones (APTA. 2011, p. 8). PPI They are initials of pixels per inch. Therefore, PPI is the measurement of the image resolution that gives insight of the size of the image to be printed. The higher the PPI value, the better the quality of the photo but up to a certain limit only. Sometimes the term PPI is confused with dots per inch (DPI) which refers to the resolution of the printing device (Chastain, 2008, p. 1). Pixels It is also known as active picture element. The term is used in cameras and it is related to the horizontal lines of resolution. Pixels are termed as the number of light sensitive elements in a camera (APTA. 2011, p. 9). A quality picture is dependent on the size and number of the digital pixels found in the image. Any digital camera has an image sensor device that contains more than a million cells that captures light. Therefore one megapixel will contain a million pixels. A large sensor will always produce a higher quality image than a lower one. The size of any image is determined by the height and the width dimensions. For example a 3500 X 2200 image means that there are 3500 pixels from right to left and 2400 pixels from top to bottom. The total number of pixels in that image will be the product of the width and height 3500 X 2200 giving 7,700,000 pixels an equivalent of 8 megapixel picture. Bayer Filter It is an organisation of colour filter arrays that arranges the colours red, green and blue on the appropriate grid of the photo sensors. The filter gives 50% green, 25% blue and 25% red hence given the initials of RGGB. Colour filters are required in that typical photo sensors have no specify in detection of wavelength of light intensity. Auto focus should be applied in surveillance cases only when the subjects are in a continuous movement near and away from the camera. This helps the camera to track the moving object at different times despite the distance between the two (Robinson, 2010, p. 135). Sometimes crime photographers’ posses zoom lenses varying from 35mm to 80mm. According to Robinson (2010, p. 128), whenever an investigator is recording a major crime scene, silver-based film with more 35mm format are the best to use. Every camera should have a high acutance whereby the camera has the ability to produce a sharp edge of the object being taken. Pre-focus before taking a crime scene image is very applicable, as an investigator, one should move the camera forward and backward until the target object is on sharp focus (Robinson, 2010, p. 137). It is advisable to capture the target object may be a fingerprint to its highest resolution rather than covering neighbouring areas that are of no use. However, sometimes, the investigator may want to cover the entire crime scene rather than the entire object only an act known as hyper focusing (Robinson, 2010, p.138). Indoor crimes investigation starts by photographing the external areas to gain a hint of how the suspect gained access into the scene. Therefore, one will need to cover a large area hence the inclusive of the thumb rule whereby 5he area in front and back is in a clear focus. However, if one discovers that the area will be out of focus, then it is advisable to exclude it to avoid any critics (Robinson, 2010, p. 139). Sometimes one may be taking an image or some evidence that are not visible in the normal light requiring the use of infra red or ultraviolet radiations. However, there is no mark within the camera to show the range of infra red radiations. What one will have to do is to focus the evidence under normal light. Foe infra red adjustment is done towards the right side while for ultra violet, the adjustment is done for the same distance but towards left side (Robinson, 2010, p. 156). Perspective Error According to Patterson (2014, p. 1), a camera man may take a photo only to realize that the photo is bent. The problem is attributed to the object and the camera. The problem is very common when taking photos of tall objects such as buildings with the lens not horizontal. According to Rowse (2010, p. 1), it is important to capture distanced scenes using a long focal length. Moreover, it is important to use a tripod stand for the camera rigidity in that even a small shake of the camera during shooting will be noticed. For example, a ground based detector will have to be very keen when taking a photograph of a broken window in a storied building where the crime was reported. The experience of the camera man will influence the information to be gathered by the camera in bringing up of the real situation and setting of the crime scene. Therefore, addition use of remote shutter is very efficient. Circles of Confusion (CoC) In optics, circles of confusion are the optical spot that is formed after light rays from the lens not converging at a point with perfect focus when imaging an object. CoC is used in the description of Depth of Field. It is the image part that is completely sharp for observance. Standard values of CoC are associated with each image format. However, the appropriate value depends on visual acuity, amount of enlargement and viewing conditions. Real lenses do not focus all the light rays into a single point, therefore, leading to an image being focused as a spot rather than a point. The smallest spot produced by the lens is called the circle of least confusion. The CoC diameter limit for the final image is referred to as the largest blur spot that will be observed and perceived by the human eye as a point (Photokonnexion, 2010, p. 1). Macro lenses They are lenses that are capable of producing life-sized images on the image sensor. They offer magnification factor of X1 or a 1: 1 at its closest focus setting. In macro lenses, the field curvature should be minimised as much as possible for sharpness and high focus. Tiny objects are enlarged using the macro lenses to create very sharp images a case example of fingerprints from a crime scene. Their enlargement using the lenses makes them visible for analysis (Jmeyor, 2013, p. 1). JPEG It is a standard format image that can be read by any image program. It is exactly eight bits per colour and 12 bits per location. Its fairly small in size hence a camera of about 8 mega pixels will produce it with a storage size of less than 3 megabytes. The image is very sharp and suitable for printing or sharing in the web with easy manipulation without data loss. Therefore, detectives can have their hard disks saving much space after taking several unlimited number of photos in crime scenes with maintenance of clarity and sharpness. When shooting in JPEG, the cameras internal software uses the sensor information and processes it before saving. However, some colour is lost, and some noises are experienced in such images (Rowse, 2006, p. 1). According to Atkins, (2004, p. 1), JPEG files are faster to take during shooting besides many of them occupying the memory card in comparison of the RAW files which require conversion into JPEG. Therefore, if one uses the correct white balance and exposure under the optimum camera parameters, high quality JPEG image will be produced. Therefore, RAW images should be taken when one is going to perform some afterward processing. If one has no clue about the right exposure and whiteness, use of the RAW format will be the best. The obtained images will be converted from 16 bits into eight bits ready for printing. Therefore, the difference between RAW and JPEG is that, in RAW, one uses more time and larger space hence lesser images in comparison of JPEG (Atkins, 2004. p. 1). Inverse square law According to Lawrence (2004, p. 1), the term ion photography relates to light during photo shooting. The law states that an object that is two times longer from the source of light will receive about a quarter of illumination. Therefore, one will need to increase the light intensity whenever moving further from the light source and the object. Therefore, the lens aperture will need to be opened further or use a powerful flash gun. Cosine law Based on Bilissi and Langford (2007, p. 400), Cosine Law states that any illumination on a flat surface, diffusing surface varies with the cosine of the angle of the incident lighting comparison of the perpendicular. In photography, this means that less light is obtained at the corners of the camera frames than at the centre. In negative or positive photography, the camera lens effect ids compensated by the cosine law (Bilissi and Langford, 2007, p. 400). The discrete cosine transformation that divides the image into blocks determines what to be safely based on perception. High compression ratio will have more part of the image thrown away (Rowse, 2006, p. 1). Photographing Fingerprints According to Finn (2008, p. 31), the camera role in photographing has remained very effective in documenting crime scene prior to the inquiry. Officers arrive at the scene and photograph the scene its setting and contents. Sites such as doors, glasses and windows among others that may reveal fingerprint are dusted; illuminate using ultraviolet radiation, infrared or any other mechanism that can make them visible. Observable prints are lifted, photographed or both depending on the prints nature. The collected prints are scanned into the automatic fingerprint identification (Finn, 2008, p. 31). The investigator analyzes the print by pointing the idiosyncratic features of the prints to view the ridges and compared them for similarities in the databases. The first step involves location of the hand and finger to determine if from right or left hand. The prints general pattern is analyzed to identify the direction into which the swirls move. The ridge characteristic is the most significance part of the process that can provide with rich information of matching the print with the stored print in the database. The lakes, dots, ridge endings and bifurcations, are unique and specific. The AFIS will present a couple of possible matches that will be compared with collected prints. If no similarity found, the prints are stored in the database for potential use in future as a source of evidence (Finn, 2008, p. 31). In general, the whole process uses many photos. The first photo of which may not be single but many of them are taken at the crime scene. The second photo will be of the identified fingerprints from the identified site in the crime scene. The third print will be a close up of the print. The third print is left on acetate and forwarded for AFIS scanning to be used for further analysis (Finn, 2008, p. 31). The AFIS will produce a matching photo similar to the latent print on the file. The third photo of a close-up image is used for identification. Enlargement of both the latent and closed-up photo are done up to a limited size of 11 inches. The matching details of the criminal record are examined (Finn, 2008, p. 32). The analysis of the photograph shows a continuity of the suspected presence in the crime scene. The camera represents and guarantees natural inference of the presence. The little information obtained from the crime scene can relate or distance the suspect from the crime. At the first stage, there may be only a single finger print to link the suspect. Moreover, several prints may be taken from any site within the crime scene. Several aggregates of the prints are, therefore, produced and stored in the AFIS databases. The obtained fingerprints may have no connection to the stored information but their storage guarantees identification in the future dates, in case of arrest or other activities such as check for employment. Therefore, the photographed prints will remain in the archives for potential identification in the future days (Finn, 2008, p. 38). Digital cameras, live scan systems, data technologies and other peripheral scanning devices have enabled the law enhancing bodies to collect and store the unlimited number of fingerprints collected from different bodies associated with crime activities. In USA only, the FBI had collected more than 35 million fingerprints. Its database had more than 630 million individual fingerprints as per 2000 (Finn, 2008, p. 39). Conclusion Whenever taking a photo, there are some items that need to be put into consideration. They include resolution, image size, lighting and the camera features. It is now evident that the photography plays a crucial role in collection and storage of evidence prior to crime activities. Therefore, it would be better if the field of camera is improved to offer more diverse and important facts in solving crimes and improving investigations. References American Public Transportation Association, APTA. 2011. Selection of cameras, digital recording, digital high speed and train lines for use in transit related CCTVsystems, [online]. Available at: [Accessed on 20 April, 2014] Atkins, B. 2004. RAW, JPEG and TIFF, [online]. Available at: < http://photo.net/learn/raw/> [Accessed on 20 April, 2014]. Baldwin, H. 2008. Oblique lighting with the ALS, [online]. Available at: < http://www.feinc.net/als.htm > [Accessed on 20 April, 2014]. Bilissi, E. and Langford, M. 2007. Langfords Advanced Photography. New York: Taylor & Francis. Chaikovsky, A., Argaman, U., Balman, A., Sin-David, L., Barzovski, A. and Yaalon, U. 2005. Multiple Exposure Method in Digital Photography of Fingerprints. Journal of Forensic Identification, 55(5), pp. 574-584. Chastain, S. 2008. PPI, [online]. Available at: < http://graphicssoft.about.com/od/glossary/g/ppi.htm> [Accessed on 20 April, 2014]. Crime Museum. 2014. Fingerprints, [online]. Available at: < http://www.crimemuseum.org/crime-library/fingerprints> [Accessed on 20 April, 2014]. Dowdey, S. 2012. How crime scene photographs work, [online]. Available at: < http://science.howstuffworks.com/crime-scene-photography.htm> [Accessed on 20 April, 2014]. Finn, J. Photographing fingerprints: data collection and state surveillance. Surveillance & Society, 3 (1), p. 21-44. [Online]. Available at: < http://www.surveillance-and-society.org/articles3(1).fingerprints.pdf> [Accessed on 20 April, 2014].  Horn, G. 2009. Camera Operator. New York: Gareth Stevens Publishing.  Houck, M. and Siegel. J. 2010. Fundamentals of Forensic Science. New York: Academic Press. Jmeyer, A. 2013. What is the macro lens? Magnification and minimum focus distance explained, [online]. Available at: < http://www.digitalcameraworld.com/2013/08/23/what-is-a-macro-lens-magnification-minimum-focus-distance/> [Accessed on 20 April, 2014]. Lawrence, G. 2004. The Inverse Square Law. [Online]. Available at: < http://www.geofflawrence.com/inverse_square_law.html> [Accessed on 20 April, 2014]. National Law Enforcement Museum. 2011. Bertillon system of criminal investigation. Insider, 3 (9). [Online] 12 November, 2011. Available at: < http://www.nleomf.org/museum/news/newsletters/online-insider/november-2011/bertillon-system-criminal-identification.html> [Accessed on 20 April, 2014]. Patterson, S. 2014. Perspective correction in Photoshop-repairing key stoning, [online]. Available at: < http://www.photoshopessentials.com/photo-editing/keystoning/> [Accessed on 20 April, 2014]. Photokonnexion. 2010. Definition: circle of confusion, [online]. Available at: < http://www.photokonnexion.com/?page_id=4373 > [Accessed on 20 April, 2014].  Robinson, E. 2010. Crime Scene Photography. New York: Academic Press. Rowse, D. 2006. RAW vs. JPEG, [online]. Available at: < http://digital-photography-school.com/raw-vs-jpeg/> [Accessed on 20 April, 2014]. Rowse, D. 2010. Shooting landscape with longer focal lengths, [online]. Available at: < http://digital-photography-school.com/shooting-landscapes-with-longer-focal-lengths/> [Accessed on 20 April, 2014]. SIRCHIE. 2014. Crime scene photography-phase 1 and phase 2, [online]. Available at: < http://www.sirchie.com/training/training-programs/crimescenephotograph-phase1.html> [Accessed on 20 April, 2014]. Smith, M. 2008. Latent fingerprinting on latex gloves: Development and Photographic techniques, [online]. Available at: < http://www.iowaiai.org/latent_fingerprints_on_latex_gloves.html> [Accessed on 20 April, 2014]. Warren, T. 2013. Smartphone Technology for Capturing Un-treated Latent Fingerprints Feasibility Research, [online] 27 August, 2013. Available at: < http://www.forensicmag.com/news/2013/08/smartphone-technology-capturing-untreated-latent-fingerprints-feasibility-research> [Accessed on 20 April, 2014]. Williams, R. and P. Johnson (2004) ‘Circuits of Surveillance,’ Surveillance and Society 2 (1): 1-14, [online]. Available at: < http://www.surveillance-and-society/articles2(1)/circuits.pdf> [Accessed on 20 April, 2014]. Appendices The figures below are explanation of the fingerprinting process. Images are courtesy of https://www.google.com/search?q=fingerprints&client Figure 1 below shows the features of a finger print. Figure 2 below shows the finger print patterns. Figure 3 below shows finger prints illumination on UV light. Figure 4 below shows matching of the lifted and latent fingerprints Figure 5 below shows how dusting is performed Figures below are photographing methods. Courtesy of https://www.google.com/search?q=photographing Figure 6 below shows photographing methods Figure 7 below shows photographing methods Figure 8 below shows photographing methods Read More