Forensic Analysis of Fingerprints

1. The Origin of Forensic Science
The general public’s fascinating with forensic science is unquestioned. Thus fascination with forensic science is not difficult to understand. Investigators today have an amazing array of instruments, equipment, chemicals and other devices with which to examine the minutest evidence. “No criminal can hope to escape from a crime scene without leaving behind at least some evidence.
One of the most important contributors to the forensic scientist’s investigative arsenal has been the science of chemistry. Researchers have developed a host of new procedures for analyzing blood, fingerprints, DNA samples, documents, ammunition, medicines and drugs, soil, bacteria and other microorganism, fire remnants and even voiceprints. The purpose of forensic chemistry is to provide an introduction to some of the most important developments in this field over the past few decades and make it possible for readers to continue the study of forensic chemistry on their own.

2. The Scope of Forensic Chemistry
The analysis of a crime scene involves the participation of experts in both the physical and biological sciences as well as in many areas of technology and law enforcement. Forensic chemists study fingerprint patterns and fiber, glass, gunshot, and other types of residues; analyze drugs and poisons; examine possible forgeries; analyze residues for possible arson and explosive crimes; and carry out DNA analyses to identify possible criminal suspects. Today the term criminalistics is often used to describe the work that forensic chemists and other forensic scientists do. The term means virtually the same as does the more common phrase forensic science.




3. Fingerprinting

When bloody finger-marks or impression on clay, glass, etc exist they may lead to the scientific identification of criminals. Fingerprints are characteristic features of human skin found on the palm side of the fingers and thumbs and on the soles of the feet. They are almost the only place on the body where the skin is not smooth. Biologists believe that fingerprints have evolved to provide the hands and feet with rough surfaces that allow one to grasp and hold objects more easily – figure 1.




4.1 History of Fingerprinting
Scientific studies of fingerprints began in the late 17th century when an English physician, Nehemiah Grew (1641 - 1712) took note of the “innumerable (too many to be counted) little ridges” that he observed on the tips of fingers. The first concrete step in that direction occurred in 1823 when the Czech physiologist Jan Purkinje (1778 – 1869) noted that fingerprints commonly followed one of nine distinctive patterns which he called transverse curve, central longitudinal stria, oblique stripe, oblique loop, almond whorl, spiral whorl, ellipse, circle and double whorl. He made no connection between these patterns and their potential use in the identification of criminals.
By 1850s, the stage had been set for the scientists and law enforcement officers to begin to see how fingerprints could use in forensic science.

4.2 General Principles of Fingerprinting
Fingerprints begin to develop and are completely formed during the fetal stage of life. They have two fundamental characteristics that permit them to be used to identify an individual
 Fingerprint pattern are unique. No two humans have been found who have identical fingerprint patterns.
 Fingerprint patterns do not change during a person’s life.
The basic structure of a fingerprint can easily be seen by means of a microscopic examination of skin pattern on the fingers, thumbs and soles of the feet. The skin in such locations is folded into hills and a valley knows respectively as ridges and grooves. The ridges are frequently referred to as friction ridges, because they provide the friction needed to grip and hold an object. Friction ridges may be of different lengths and shapes. In the fingers and thumbs, these ridges form pattern of loops, whorls and arches – figure 2.




Rid geology study of the uniqueness of friction ridge structures and their use for personal identification .

In the loop pattern there are two focal points: the core or the center of the loop and the delta. The delta is the area of the pattern where there is a triangulation or a dividing of the ridges. When recording fingerprints, the delta and the area between the delta and the core must be completely recorded.


The whorl pattern will have two or more deltas. For whorl pattern, all deltas and the areas between them must be recorded . the arch pattern has no delta or core; but it too must be fully recorded so that its individual characteristics can be easily distinguished.


Scientists have now identified more than 150 different ridge characteristics (also known as minutiae) by which two fingerprint patterns can be compared with each other. For example, the ridges in a fingerprint pattern may be long in some place and short in another. They may be broken into short segments known as islands.

the most obvious features of a fingerprint are raised area (ridges) and depression (grooves) "Forensic chemistry by David E. Newton, published 2007 page 16"
They may branch at some point in their length, producing bifurcations and they may fold around upon themselves forming closed loops. One problem with the process of fingerprint identification is deciding how many of those 150 characteristics must match in order for the prints to be identical. Some of the characteristic are listed in figure 3. Standard set by some countries are as follow:
 UK: normally require two points to match on 16 point system in order for them to be considered identical.
 Australia and New Zealand: deals with a 12-point system.
 India: deals with 8-point system
 USA: every state has its own point system but the FBI deal with 12-point system.

Fingerprints may take one of the three forms: visible, plastic or latent.

 Visible prints are left behind when a person transfers some type of colored material on his or her hand to a smooth surface by touching it. For example, a person’s hands might become bloody during commission of a crime. That blood would then be left behind on any surface the individual touched, such as a door handle, tabletop, or automobile steering wheel.

 Paint, grease, dirt, ink, or other materials are also commonly found in visible prints.

 Plastic prints are produced when a person touches a soft material, such as clay, mud, soap, or wax, in which the friction ridges produce a visible pattern. Latent prints are so called because they are invisible to the human eye. They are composed of eccrine secretions, produced by small sweat glands located just under the surface of friction ridges. Eccrine secretions are left behind after a person has touched an object. The vast majority of fingerprints that law enforcement officers deal with are latent prints. A number of chemical techniques have been developed by which such prints can be made visible and, therefore, usable for purposes of identification.

4.3 Fingerprint Detection
The use of fingerprint patterns to arrest and convict criminals has become a highly sophisticated, often complex procedure that makes use of the best tools available in the physical and chemical sciences.
One of the most important variables affecting fingerprint identification (other than the prints themselves) is the kind of surface on which the prints are deposited. The procedure chosen for detecting and studying a print depends on whether the surface on which it was deposited is rough or smooth, porous or nonporous. In porous surfaces, the materials that make up the fingerprint (water and solids found in eccrine secretions) may soak into the material and migrate away from the area where they were left. A nonporous surface does not present this problem. Fingerprint detection usually involves three major steps: locating the print, developing and/or enhancing its properties for better viewing, and protecting and preserving the print.


The basic principle behind fingerprint detection is the following:
When a person touches a surface with his or her finger(s), a small amount of eccrine secretions from sweat glands on the hand is left behind on the surface, the fingerprint. That residue typically consists almost entirely (98.5 percent) of water, in which are dissolved small amounts (1.5 percent) of a large variety of solids. About two-thirds of the solids are organic substances, while the remaining one-third is inorganic. The chart below lists some of the chemicals typically found in eccrine secretions. Although many of these substances are present in very small amounts, they are important because they may serve as the basis for some characteristic chemical reaction by which they, and therefore the fingerprint itself, may be detected.
`Chemicals commonly found in eccrine secretions
Organic Inorganic
o Amino acid Water (more than 98%)
o Urea chlorides
o Uric acid Metal ions
o Lactic acid Sulfates
o Monosaccharide & Disaccharides Phosphate
o Creatinine Ammonia
o Choline
Table 1 chemicals found in eccrine secretion, "Forensic Chemistry by David E. Newton, published 2007, page 18
4.3.1 Powder Tests
A latent fingerprint can be detected in any of three ways: with powders, by means of chemical tests, and by using optical procedures. These tests are designed primarily for the detection of latent prints since visible and plastic prints typically do not require further enhancement to make them visible.
In the first procedure that is often used in the search for latent prints, the person collecting the print spreads a colored powder on it such that some of the powder adheres to the print, making it visible. The use of a powder is possible only when a relatively large amount of eccrine secretions has been deposited on a surface, at least 500 ng (ng = nanogram, 1 billionth of a gram). The normal procedure is to sprinkle the powder on a camel’s hair, nylon, or other fine-haired brush and then to wipe the brush gently across the surface being tested.



4.3.2 Chemical Tests
The second method of fingerprint detection invokes some type of chemical test that results in the formation of a characteristic colored product. Chemical tests are more sensitive than powder tests and can generally be used with residues that weigh between 100 and 200ng. Some of the most widely used chemical tests are the silver nitrate, iodine fuming, ninhydrin, and superglue (cyanoacrylate), Physical Developer, and ruthenium oxide tests.
• One of the oldest methods for the detection of latent fingerprints makes use of silver nitrate (AgNO3). The test depends on the fact that silver nitrate reacts with the chloride ion present in eccrine secretions:
AgNO3(aq) + Cl-(aq) AgCl(s) + NO3-(aq)
When exposed to light, solid silver chloride readily decomposes, forming chlorine gas and solid, grayish silver metal: To perform the silver nitrate test, the tester sprays or gently wipes a small amount of a 3 percent solution of silver nitrate across the surface being examined for fingerprints. The surface is then exposed to ultraviolet light or, if that is not available, to bright normal light. Any fingerprints on the surface will become visible as a grayish pattern in a matter of minutes.
2AgCl(s) + hv 2Ag0(s) + Cl2(g)
The silver nitrate test is used less frequently today than previously partly because the prints formed with the process tend to become blurred over time and are not usable with prints more than a few weeks old.
• Another popular and widely used test for latent fingerprints is the iodine fuming test. When iodine crystals are heated, they sublime; that is, they pass directly from the solid to the vapor state without first melting. In the presence of eccrine secretions, the iodine reacts with fatty acids in the secretions, forming a brownish complex that is easily visible. The complex decomposes rather easily, however, and the brownish evidence of any prints present on a surface fades rather quickly.
The test is conducted by suspending the surface on which prints have been deposited in a closed container. Iodine crystals are heated in a separate container called an iodine fuming gun, and the vapors produced are passed into the closed container. The container must have a transparent front so that the results of the test can be easily seen and photographed. Any prints detected in this way can be “fixed,” or made more permanent, by introducing a second reagent into the container. One substance commonly used is a starch solution, which reacts with iodine deposited on the prints to form a more permanent blue pattern.
• Ninhydrin is an aromatic compound whose systematic name is triketohydrindene hydrate. In 1910, the English chemist Siegfried Ruhemann (1859–1943) discovered that ninhydrin reacts with amino acids to form a distinctive purple compound now known as Ruhemann’s purple – figure 10. The test is conducted with a solution of about 0.5 percent ninhydrin in some appropriate solvent (such as ethanol or acetone). A number of different formulations are commercially available under names such as Arklone and Fluorisol. The solution is sprayed on the surface on which prints are suspected, and the appearance of the distinctive purple color is evidence of the existence of such prints. Color may begin to develop within a few hours or as long as 48 hours after application of the ninhydrin. Development of a ninhydrin print is also enhanced by heat treatment. The print-containing surface may be suspended in a heating oven at temperatures of up to 100°C for up to about five minutes.
Reaction mechanism:


The results of a ninhydrin test can be further enhanced and, in some cases, preserved by the addition of a second reagent. Spraying the print-containing surface with a salt of zinc, for example, causes a color change from purple to orange. In some cases, the color change permits the print pattern to stand out more clearly from the background than the original Ruhemann purple. The ninhydrin test has now become the most popular test for latent fingerprints on paper. It has been used successfully in detecting prints that are up to 15 years old. Ninhydrin is by no means the only reagent that reacts specifically and characteristically with amino acids, however. A considerable amount of research has been conducted on analogs of ninhydrin, compounds with a chemical structure similar to that of ninhydrin and possessing a similar tendency to react with amino acids. Some of the compounds studied in this line of research produce results superior to those obtained with ninhydrin itself in fingerprint identification. These include benzo(f)ninhydrin; 1,8-diazafluoren-9-one (DFO); 5-methoxyninhydrin; and 5-(methylthio)ninhydrin.
.
• A popular commercial adhesive sold under the name of superglue has been shown to be an effective reagent for the detection of fingerprints. The primary ingredient of superglue is generally the methyl or ethyl ester of cyanoacrylic acid, methyl-2-cyanoacrylate or ethyl-2-cyanoacrylate. When superglue is heated, it produces a colorless vapor that appears to be especially attracted to oily products such as those generally found in a fingerprint. The vapor deposits on the ridge patterns of the fingerprint, polymerizes, and forms a white powder (polycyanoacrylate) that adheres to the prints.
The cyanoacrylate fuming test is easy to conduct. The object to be tested is suspended inside a container with at least one transparent side figure 11. A few drops of superglue or similar cyanoacrylate product are added to the container, and the container is sealed and heated to about 100°C. That heat is sufficient to cause vaporization and polymerization of the cyanoacrylate, resulting in the formation of distinctive white print patterns, a process that may take two hours or more. The cyanoacrylate fuming test has become the procedure of choice for the detection of latent prints deposited on nonporous objects, such as glass, plastic, rubber, and leather. As with other methods of latent print detection, the prints obtained by means of the cyanoacrylate fuming test may be further enhanced by a variety of techniques for better viewing. They may be sprayed with a variety of dyes, such as gentian violet, basic yellow 40, basic red 28, rhodamine 6G, or thenoyl euoprium chelate. Sometimes the dye simply intensifies or otherwise improves the appearance of the print. Gentian violet, for example, combines with the white polycyanoacrylate powder deposited on a print to produce a deep purple. In other cases, the dye improves the fluorescence of the prints under the with Rhodamine 6G, for example, fluoresce strongly in the green region of the electromagnetic spectrum optical source. Prints treated with cyanoacrylate and then sprayed with Rhodamine 6G, for example, fluoresce strongly in the green region of the electromagnetic spectrum. A product that has some important special applications in fingerprint identification is Physical Developer (PD). The primary active ingredient in PD is silver nitrate, a substance that reacts readily with chloride ions in eccrine secretions, as discussed earlier.
Super Glue is approximately 98 to 99 percent cyanoacrylate ester, and it's this chemical that actually interacts with and visualizes a latent fingerprint. Cyanoacrylate ester fumes can be created when Super Glue is place on absorbent cotton treated with sodium hydroxide or by heating the glue. The fumes and the suspect material are contained within an enclosed chamber for up to 6 hours.


• The Physical Developer test has two special advantages. First, it works well with porous objects that are wet or that have been wet in the past. Second, PD has been effective in developing prints when other methods have been unsuccessful. The greatest disadvantage of the PD test, however, is that it is destructive. The chemicals in the product may wash away parts of the print itself or may react with the surface to which they have adhered. It must, therefore, be the final test carried out on a sample.
Latent fingerprints occur on such a wide variety of materials and under such a wide variety of circumstances that specialized tests can sometimes produce results that more traditional procedures (such as ninhydrin, cyanoacrylate, and silver nitrate tests) might miss. For example, dimethylaminocinnamaldehyde (DMAC) has been used for the detection of prints left on thermal paper, a material that has posed problems with other detection systems. DMAC reacts with urea in eccrine secretions to produce a dark red product. Another test showing some promise has involved the use of ruthenium tetroxide (RuO4). Since ruthenium tetroxide presents certain safety hazards (it tends to decompose explosively above 200°F [100°C]), historically its use has been quite limited. In 1995, however, a team of Japanese researchers developed a safe method by which the reagent can be used. It is now available in that formulation under the name of RTX. When a material is exposed to RTX fumes, any fingerprints on it will react with the reagent to produce a dark gray image. The reagent has proved to be especially useful on certain types of porous materials, such as paper money, that pose problems for other types of detection systems.

4.3.3 Light Tests
Fingerprints that are normally not visible under ordinary light may often be seen if the light or the object being viewed is modified in some way. One of the simplest modifications of light to reveal a latent print is simply to shine a strong line source at an oblique angle to the surface. In some cases, this change in the direction of light alone may reveal a print that was otherwise not visible. In other cases, using a different type of light source may reveal prints. An instrument known as the Reflected Ultraviolet Imaging System (RUVIS), for example, emits an ultraviolet light that is directed at a surface suspected of holding latent prints. Prints otherwise not visible in ordinary light may become visible under the ultraviolet beam.

One of the most important of these developments was the discovery that traditional fingerprint tests (such as the ninhydrin or cyanoacrylate test) could be made more useful by adding a second chemical to a print being examined to make it fluorescent or to enhance its fluorescence. Some common examples are the use of zinc or cadmium chloride following the ninhydrin test and the use of rhodamine 6G after the cyanoacrylate test. Another important discovery was the finding that lasers are not required to produce luminescence; in fact, ordinary light is often satisfactory for developing or enhancing fingerprints. The primary requirement is that the light must be sufficiently intense to cause a print to fluoresce visibly. A variety of such light sources has been tried, and many have become part of the forensic scientist’s crime-detection arsenal. High-intensity light sources used for the fluorescence of latent prints are commonly known as forensic light sources. The search for new methods of detecting, enhancing, and preserving fingerprints continues in forensic science. There are always opportunities for discovering methods of uncovering prints that cannot be easily found by existing methods or for improving the efficiency of methods that have been known and used for long periods of time.
With these various methods, the one chosen depends on the surface to be worked on. Powders should be selected when the surface is smooth, while chemicals for soft and porous surfaces. When attempting to utilize all of the chemical methods of development, one should use iodine fuming first, ninhydrin second, then silver nitrate, and finally super glue fuming if it applies. This is the procedure for optimum visualization because iodine fuming is not permanent, and if ninhydrin fails, silver nitrate can be used but will wash away all the fatty oils and proteins from the surface. Hence, silver nitrate is used last if super glue fuming is not used.











5 DNA fingerprinting
DNA fingerprinting is a method by which the DNA pattern of an individual is compared against DNA from blood, semen, or other bodily materials collected at the scene of crime. Since every person’s DNA pattern is unique (except in the case of identical twins), a DNA fingerprint match is as close to an absolute identification as forensic scientists are likely to achieve.
Fingerprint analysis is based on the assumption that no two individuals have exactly the same set of digital fingerprints. DNA is an abbreviation for the term deoxyribonucleic acid, a group of biochemical compounds found in the cells of nearly all living organisms. These compounds carry the genetic code that tells cells what functions they are to perform; thus they are arguably the most essential of all biochemical molecules. They also provide the mechanism by which this information is transmitted from generation to generation.
DNA molecule consists of two long strands wrapped around each other in a geometric conformation known as double helix. The two strands are bonded loosely to each other by means of hydrogen bonds between adjacent units on each strand. The long spaghettilike strands that make up DNA consist of repeating units know as nucleotides. Each nucleotides consists of three units: the sugar deoxyribose, a phosphate group and one of four nitrogen bases. Two of the four nitrogen bases present in DNA, cytosine and thymine are derivatives of the nitrogen base called pyrimidine and two adenine and guanine are derivatives of the base know as purine.


In DNA molecule, the two complementary strands are arranged with the sugar-phosphate backbone of the strand on the outside of the double helix, and the projecting nitrogen bases facing inward, adjacent to each other. These bases are not arranged randomly; they are paired according to a specific chemical rule:
 A purine base may align itself with a pyrimidine base only and vice versa. That is, the only pairings of nitrogen bases permitted are those in which a guanine (G) on one strand as aligned with a cytosine (C) on the opposite strand and those in which an adenine (A) on one strand is matched with a thymine (T) on the opposite strand.

5.1 Applications of DNA Testing
Variation in DNA are probably the single most reliable measure of genetic diversity. Organism whose DNA differ dramatically have the greatest physical and biological diversity, while those whose DNA differ only moderately and relatively similar in their physical and biological characteristics. Scientists believe that the human genome contains about 80,000 distinct genes. Each of these genes contains several thousand nucleotides. The availability of DNA maps makes possible a number of applications, including some of the interest to relatively small number of researchers and others of considerable practical value to many scientists and other professionals.
The basic for this conclusion is that DNA is normally transmitted conservatively (without error) from parent to offspring. The DNA in an organism’s all is usually identical to that found in the cells of its parent’s bodies. That general rule is violated only when mutations occur. A mutation is a change in DNA sequences cause by burst of energy (such as x-ray), certain chemicals, or other factors. For example, a photon of radiation might strike a DNA molecule; rupture a bond within a nucleotide, and cause a change in nucleotide sequence.
The first and one of the best-known fields in which DNA typing was used is paternity testing. Although it is always clear who the mother of a child is, there is sometimes a question as to who the child’s father. The DNA argument for paternity is simple, it is based on the fact that DNA is passed on conservatively (without change) from generation to generation. Thus, a child’s DNA is some mixture of both parents’ DNA.
5.2 Forensic DNA Typing
DNA typing is a clearly powerful tool with numerous applications. In forensic science, it is used for the identification of individuals accused of rape, murder and other violent crimes. Such applications are possible because DNA in such crimes is usually available from three essential sources: the victim, the perpetrator of the crime, and evidence left behind at the scene of the crime, such as blood, semen, hair or other biological materials. Forensic DNA typing generally involves the comparison of three kinds of DNA as shown below – figure 13:
















DNA typing can be determine conclusively(1) whether evidence at the crime scene, such as blood, hair or other biological materials came from the victim or if not (2) whether it came from some other known or unknown individual.




5.2.1 Procedures
Two technologies are currently in general use for the analysis of DNA patterns: restriction fragment length polymorphisms (RFLP) and polymerase chain reaction (PCR).
Steps:
• First, the DNA sample must be removed from the material on which it was deposited (a shirt, carpet, floor, victim’s skin, or other body part, for example).
• It must then be cleaned and separated from non-DNA materials that would contaminate the analysis.
• It must also be examined to determine the amount of DNA present and its integrity, meaning the amount of DNA that remains intact.

Organic extraction is perhaps the simplest and most common method for removing a DNA sample from the material on which it has been deposited. In this procedure, a piece of the material is cut from the whole object (a garment or carpet, for example) and added to a flask containing an organic solvent—usually phenol, chloroform, isoamyl alcohol, or some combination of these solvents. The flask is then warmed, increasing the rate at which cells in the sample are released from the material and dissolved in the solvent. When removal of the biological material from the sample appears complete, the cells obtained are transferred to a second flask and mixed with another reagent, such as EDTA (ethylenediaminetetraacetic acid), sodium dodecyl sulfate, or tris [hydroxymethane]amino methane. This reagent causes the lysis (rupture) of cells, releasing pure DNA, which can then be concentrated and collected for further study.
The presence of sperm cells on a piece of evidence may complicate the extraction procedures just described. Sperm cells are more resistant to attack than other cells, requiring a modified approach to extraction. In this approach, the piece of evidence containing both sperm and non sperm cells is exposed to organic extraction, as already described. That extraction removes both types of cells from the material on which they are deposited. The resulting mixture is then centrifuged, causing it to separate into a clear solution containing non sperm DNA and a clump of material at the bottom of the centrifuge tube containing precipitated sperm DNA. The two components can then be separated and treated with distinct reagents suitable for the lysis of each type of cell.

A second technique for assessing the amount of DNA present in a sample is called a yield gel. A yield gel consists of a solid platform (a support system; for example, a piece of plastic) covered with a thin layer of agarose gel, made by heating and then cooling agar, a colloidal extract of algae. A row of indentations (wells) runs parallel to the top of the platform. One or more samples are placed into each of these wells along with a number of standards. The standards consist of DNA samples of known size and complete integrity. An electrical potential is then applied to the agarose gel, drawing DNA fragments downward through the gel. After some period of time (usually less than an hour), the agarose gel is treated with the reagent ethidium bromide (EB). EB binds with double-stranded nucleic acids and fluoresces when exposed to ultraviolet light. The pattern of fluorescing spots on the agarose gel can then be photographed and/or analyzed by colorometric means to determine the amount of double-stranded DNA present.
The pattern formed in a yield gel also provides information about the integrity of DNA in a sample, because the larger a DNA molecule, the larger and more intense the spot of light it produces and the closer that spot is to its point of origin at the top of the gel. By contrast, a degraded piece of DNA produces a larger, less well-defined, less visually intense spot of light that has migrated downward from its point of origin to a greater degree. Because EB bonds only poorly with single-stranded DNA, severely degraded DNA consisting of such structures will be only poorly visible, or not visible at all. The advantage of a yield gel is that it provides evidence as to the integrity of the DNA sample, that is, the extent to which it has or has not been degraded. Its disadvantage is that it does not distinguish among DNA from a variety of species.









6 Conclusion
Chemists have made a number of important contributions to forensic science over the past two centuries. When criminologists recognized the value of fingerprints as a reliable means of identifying individuals, they began to search for methods by which prints could be collected and interpreted. They drew on a number of chemical procedures—some already in existence and some invented for the purpose of fingerprint identification—to improve the use of fingerprinting as a forensic technique. Out of this research grew procedures such as the silver nitrate, iodine fuming, ninhydrin, and superglue tests and procedures such as small particle reagent analysis and vacuum metal deposition.
For all of the progress made by forensic chemists, however, nothing quite matches the development of DNA typing as a method for identifying individuals. The procedure has an advantage over fingerprinting in that it rests on a certifiable and provable scientific basis. It also surpasses all other forensic tests in the degree of sensitivity, with the ability to identify individuals with a probability of one out of a million or better. Little wonder that most forensic scientists acknowledge that the gold standard of identification is likely to be DNA typing for the foreseeable future.

















Bibliography

1. Forensic Chemistry “ Facts on File Science Library” by David E. Newton; published 2007 pp 11 – 31 & pp 131- 168

2. http://www.enote.com

3. http://www.detectopoint.com

4. http://www.cc.columbia.edu/cu/cup

5. http://www.scribd.com


6. http://www.fbi.gov