Forensic powder

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Securing evidence with iron filings (Magna Brush)

Latent fingerprints are made visible through the dusting process or through the action of chemical substances. The use of contrast powder is particularly useful for fresh fingerprints. It uses the fact that the substances transferred through the skin have a different adhesive capacity than the surface of the trace carrier. However, this ability is not retained indefinitely: water and fatty acids are subject to an evaporation process that is influenced by external factors (heat, air movement, dryness) and the nature of the trace carrier (rough or porous surface).

Various brush types are available for the dusting process . Basically only very soft brushes are used, e.g. As the squirrel hair - and the marabou -Brushes. The Zephyr brush made of the finest glass fibers has proven itself very well (more than 1,000 fiber bundles made of over 100 individually treated glass fibers). Its most prominent properties are its ability to absorb and hold sufficient amounts of powder, its long life and the fact that the fiber ends become increasingly soft with use. Chemical processes are mainly used for older fingerprints. The agents lead to a chemical reaction in the sweat substances that are still present and make the trace visually visible.

Other fat prints, such as those from the forehead or an ear, can also be made visible. These prints can not be used to clearly identify the perpetrator , but in this way the course of events can be reconstructed and locations for further evidence can be found. The choice of the means of securing evidence depends on the circumstances of the individual case.

Soot powder

  • Soot powder: The most common means of making latent fingerprints visible is soot powder . It consists of powdered carbon and has good adhesive properties. The powder is applied to the trace carrier with a dust brush or atomizer until sufficient contrast is achieved. It can also be sprinkled on the track carrier and moved by shaking or rolling. Excess powder is removed with a separate dusting brush, shaken off or tapped off. The friction between the dusting brush and the surface of the trace carrier must be kept as low as possible. The fingerprint made visible is peeled off with a transparent adhesive film and stuck on white paper (crime scene map). If the first film print is too intensive, further prints can be made if necessary. The disadvantage of carbon black powder is that there is no contrast on dark-colored trace carriers. Soot powder can be mixed with other substances. A mixture of soot and iron (III) oxide does not smear so easily with moist traces, a mixture of soot and Lycopodium is suitable for fatty traces.
  • Carbon black - iron oxide: This mixture consists of five parts of carbon black and one part of powdered iron (III) oxide . It has a higher specific weight than carbon black powder and has a somewhat stronger bond. The addition of iron oxide gives the powder a reddish-brown color. The trace is made visible and secured in the same way as with soot powder.
  • Carbon black - rice starch: The mixture consists of one part of carbon black and three parts of rice starch . The mixture is “drier” than the carbon black powder because the starch absorbs the moisture more strongly. The trace is made visible and secured in the same way as with soot powder.

Argentorat

Argentorat is a silver-colored, industrially produced aluminum powder with a very high degree of fineness; it can also be mixed with iron or copper powder . Argentorat "smears" easily; this can destroy the track. It is applied with a dust brush or atomizer, better with the Marabu atomizer. As little powder as possible should be evenly distributed. Argentorat works well for traces with little substance and for older traces, less good for fresh and / or moist traces. The addition of iron powder or copper powder causes a color change to brownish or reddish. When using a black adhesive film, the track appears the wrong way round, so it must be photocopied over.

Cyanoacrylate

The vapors of the cyanoacrylate (colorless) polymerize on the object placed in the vapor space, i. H. they combine with the natural surface moisture of the trace carrier and the residual moisture of the dactyloscopic trace. Cyanoacrylate is suitable for all kinds of plastics , metals , glossy paper, fine leather and for smooth, lacquered or sealed surfaces. It is unsuitable for lane carriers that must not be impaired. The application takes place in a steaming chamber. The substance has enormous adhesive power, and its fumes cause irritation of the mucous membranes. The process can produce an ignitable mixture of air and steam. The securing of evidence takes place photographically; for this purpose, the trace can also be enriched with a contrast medium (e.g. Manoxol molybdenum or gentian violet ). A foil removal is only possible to a limited extent (with black foil). In a newer, powdery variant of cyanoacrylate, fluorescent agents are already included. This variant is particularly suitable for use on white or multi-colored trace carriers.

acetic acid

The oxidation of the trace carrier by vapor deposition with acetic acid causes the formation of an existing trace. It is well suited for copper , brass , aluminum and other metal alloys. To search for clues, acetic acid is placed in an (acid-proof) vessel. The trace carrier is exposed to acetic acid vapor. Acetic acid vapor deposition is a contact-free and therefore trace-friendly process. However, it requires a longer examination time because one has to wait for the oxidation to develop. Evidence must be obtained immediately using a photo.

Fingerprints on adhesive tape

  • Soot powder / detergent mixture (RSM): 70 g of water, 30 g of detergent and 6 g of soot powder are stirred into a vessel to form a slightly liquid mixture and applied to the sticky surfaces of adhesive tapes, stickers or labels with a fine squirrel hair brush . The excess material is rinsed off under running water.
  • Sticky-Side Powder ™ (SSP): Sticky-Side Powder ™ is used to secure fingerprints from the sticky sides of adhesive tapes and labels. Excellent results were achieved with adhesive tape, adhesive bandages, plastic surgical tapes, clear plastic tape, packaging labels, double-sided tape, reinforced packaging tape and adhesive edges from 3M ™ Post-it-Notes. Bad results were obtained when using black electrical tape (due to poor contrast), some paper labels and adhesive tapes and labels with dried out adhesives. Approximately equal amounts of water, Photo-Flo 200 and SSP are made up in a small glass or beaker; a thin consistency should be achieved to paint . Using a small brush or a fingerprint brush, the liquid mixture is applied to the adhesive side of the tape or label. After an exposure time of 10 to 15 seconds, rinse with water. The tape can be rinsed under running water, but the preferred method is to gently do it in a bowl of water. If the solution has been on for too long, it will be difficult to remove. An alternative method for processing tapes and labels that are not suitable for the painting process is a soak process . SSP is placed in a bowl with water and the tapes are inserted with the sticky side up. The floating particles of the Sticky-Side Powder ™ are deposited on the belt. This process can take some time for the latent prints to develop. The backup is made by photographing the latent prints.

Soot

Flame soot is well suited for trace carriers that do not accept dust, e.g. B. chrome or galvanized surfaces and some plastics. Soot-generating substances are set on fire to search for traces ( pine chips , camphor , magnesium , kerosene , certain polyester resins , petroleum ). The trace carrier is held in the soot plume until the surface is sooty (do not hold too close to the flame). After cooling down, the soot is carefully removed with a Marabu pen, gently and with care, until the trace is clearly visible. Procedure: Approx. 40 ml of kerosene is poured into an evaporation dish, a piece of slightly crumpled paper is placed in it and ignited in the fume cupboard. At a distance of approx. 10 cm, the trace carrier is moved back and forth over the heavily sooting flame. Avoid direct contact with flames or overheating. The fingerprints are developed after approx. 5 minutes : Excess soot is removed by carefully wiping with a cotton ball. Observation and evaluation: After removing the excess soot, fingerprints are clearly visible as a black line pattern. During combustion, petroleum, heating oil or kerosene are only partially oxidized. Elemental carbon is created in the form of visible soot particles, which are deposited on the entire surface of the trace carrier. Due to the greater adhesion to the greasy components of the fingerprint traces, the soot sticks to the prints and clearly highlights them in the form of a color contrast. The track is secured in the original (cover with foil to protect it), photographically or by means of foil removal.

Fluorescent powder

Fluorescent powder is mainly used in the laboratory. It is well suited for trace carriers with a disturbing background (colors, patterns, e.g. bank notes or checks). The UV powder is poured onto the trace carrier. Unnecessary parts are knocked off, then the trace carrier is irradiated with UV light in complete darkness. Contact exposure takes place through special film material. The fluorescent powders, such as Redwop ™ and Greenwop ™, are Lycopodium-based and specially designed to be excited by relatively monochromatic light sources that emit blue-green light. All of these powders work very well with copper vapor and Nd: YAG lasers . They can also be used successfully with simple ultraviolet lamps. It is recommended that you use a feather brush to apply these powders. The feather brush applies the powder in a thinner, more controlled layer than when using other types of brushes. The special cohesive buffer effect of the Lycopodium carrier tends to allow the powder to “flow” over the peaks and valleys of the structured surface that would otherwise be “painted” using conventional powders. Each color of the powder fluoresces at slightly different wavelengths, so that two alternatives are offered in the event of problematic background fluorescence. Surfaces such as grained dashboards, textured surfaces, wood paneling, and similar surfaces are particularly suitable for examination with fluorescent powders. For trace carriers that are highly reflective or already fluoresce themselves, fuse powders with anti-Stokes pigments can be used, which emit light in the visible range when irradiated with IR light. The treated track is thus “glowing” under IR light, while the IR light reflected from the surface cannot be perceived by the human eye.

Gentian Violet (Gentian Violet)

The mixture is made up of 50 ml of ethanol , 10 g of phenol , 5 g of crystal violet and distilled water ; it causes a chemical reaction with some components of the dactyloscopic trace. Gentian violet is well suited for adhesive surfaces (e.g. adhesive tapes, adhesive films, adhesive labels, stickers, adhesive strips on envelopes, postage stamps, etc.) as well as for contrasting traces on light-colored trace carriers after cyanoacrylate vapor deposition. The trace carrier is dipped into the solution or moistened with a brush or sprayed with the sprayer. The treated area is immediately rinsed under running cold water. Evidence is secured in the original or photographically.

Indandione

1,2-indanedione is used to develop fluorescent fingerprints on porous materials such as paper. The compound reacts with amino acid residues to produce highly fluorescent fingerprint images. The reagent is applied to the trace carriers as a solution with ethanoic acid and ethyl acetate , the treated objects are heated at an ambient temperature of 100 degrees Celsius and stored in the dark. The fingerprints are recorded with digital images using forensic light . Photolysis of the fluorescent fingerprints was observed. Storage in the dark reduces degradation and extends the life of the fingerprints, while other chemical methods of stabilizing the fingerprints have not proven successful.

Iodine

  • Iodine powder: When iodine powder is pulverized iodine crystals without any additives, which causes a brown coloration of the track in different thickness. Crystalline iodine changes into a gaseous state at room temperature. The resulting iodine vapors accumulate on the fatty substances of the fingerprint and make the papillary lines visible in a brownish color. It represents a strong risk of corrosion for other metal devices and must therefore only be stored in gas-tight containers. The vaporization takes place in a closed glass vessel (iodination device); it can be accelerated by heating the bottom of the vessel. Iodine powder is well suited for paper , documents and trace carriers that must not be impaired, as well as for the covert (secret) search for clues. It is not suitable for trace carriers with a red-brown surface. The iodine powder is sprinkled on the trace carrier and distributed with a fine brush if necessary. If the trace is well developed or the trace becomes discolored, the process is stopped and the excess powder is removed. Securing is done photographically or by fixing the track on the track carrier. For short-term fixation, the trace carrier can be placed between two panes of glass (tape the edges). The same effect is achieved by adding potato or rice starch . Long-term fixation can be achieved by sticking a transparent film on the front and back, as well as a starch-containing film. It is unsuitable for art paper, glossy paper and trace carriers with a red-brown surface. Subsequent use of ninhydrin, silver nitrate and the adhesion process is possible.
  • Iodine - iron oxide (iodine caput mortuum ): The mixture consists of one part iodine powder and five parts iron (III) oxide (caput mortuum). It is well suited for paper as well as for traces that should be permanently fixed. The mixture is not suitable for ferromagnetic surfaces; it must not be used for magnetic image, sound and data carriers. It is used in the same way as with iodine powder. The addition of caput mortuum leads to a reddish to reddish-brown coloration and ensures reliable long-term fixation. Ninhydrin and silver nitrate can then no longer be used.
  • Iodine - potato starch: The mixture consists of one part iodine powder and ten parts potato starch . It is well suited for paper, documents and trace carriers that must not be impaired. It is used in the same way as with iodine powder. The addition of the potato starch causes the trace to be fixed briefly (approx. One week) and then recede. Ninhydrin and silver nitrate can then still be used.
  • Iodine - rice starch: The mixture consists of iodine powder (one part) and rice starch (ten parts). It is well suited for paper, documents and trace carriers that must not be impaired. It is used in the same way as with iodine powder. The addition of rice starch causes the iodine trace to turn black and causes the trace to be fixed briefly (approx. 1 week) and then recede. Ninhydrin and silver nitrate can then still be used.
  • Iodine - silver: The iodine-silver process is a dactyloscopic search for traces of human skin. The trace carrier is vaporized with iodine , then a silver plate is pressed onto the skin. The trace image develops as silver iodide on this plate, but quickly evaporates again and must therefore be photographed immediately.
  • 1,5-iodine-7,8-benzoflavone: The solution is well suited for fresh traces on smooth surfaces, for neobond paper and for smooth, untreated wood. It is sprayed onto the trace carrier (under a hood or outdoors). Existing traces are immediately visible and are fixed so that they cannot be smudged. The backup is made in the original or photographically. Some components of the solution are harmful and flammable.

Lycopodium

Lycopodium consists of bear moss spores . It is well suited for traces of little substance (e.g. on burnished weapons) and for older traces. The track is secured in the same way as with soot powder. It is important to ensure that as little powder as possible is applied.

  • Argentorat - Lycopodium: The mixture consists of one part Argentorat and fifteen to twenty parts Lycopodium. It is well suited for traces of low substance and for older traces. The addition of Lycopodium causes a certain "drying effect". The substance appears drier with less risk of smearing, but still has good adhesion. The track is secured in the same way as with Lycopodium.

Magnet powder (Magna-Brush)

Magna brush powder consists of iron or nickel and is available in different color mixtures: deep black, black, gray and silver. This makes it possible to adapt the securing method to the color of the substrate. The powder sticks like a brush to a magnetic stick and can be carefully distributed on the track carrier by wiping back and forth evenly. Only the powder particles held by the magnetic rod may come into contact with the surface to be treated. Excess powder is removed with the empty magnetic stick. The Magna Brush powder is coarser than carbon black powder (mixtures); as a result, there is a risk of mechanical damage to the track. It is well suited for rough and porous surfaces; it is not suitable for very smooth and ferromagnetic surfaces. It must not be used on magnetic image, sound and data carriers. When using magnetic powder with nickel components, a health hazard cannot be ruled out. The track is secured in the same way as with soot powder.

Malachite green

Malachite green causes a chemical reaction (green color) with components of blood or blood water, which was transferred to a trace carrier as a dactyloscopic trace. It is suitable for traces left by the transfer of blood or blood water (however the method is not reliable). The solution is harmful to health and must therefore only be used under a hood and / or with a full face mask. The securing of evidence takes place in the contact moistening process: The back of a trace card is strongly moistened with the solution and then pressed onto the trace carrier with the ball of the hand. When removing it, make sure that any blood substances that are carried away are removed immediately. In the subsequent photograph of the imprint on the trace map, the trace appears the wrong way round (on the trace carrier the wrong way round). Malachite green can also be used to increase the contrast of a trace of blood that has been treated with dusting agents and peeled off with adhesive film (moisten the back, wait for the color reaction). Since the solution also reacts to iron, dusting agents containing iron can also produce color reactions.

Manganese dioxide powder

Manganese (IV) oxide (also manganese dioxide or brownstone) is produced industrially and is dark gray in color. The generation of dust is lower than with the soot powder mixtures. The powder is well suited for metal trace carriers (if Magna-Brush is not applicable). The manganese dioxide powder can also be used as a mixture with carbon black powder in a ratio of three to one. The trace is made visible and secured in the same way as with soot powder.

Manoxol molybdenum

The molecules of the manoxol- molybdenum mixture are deposited on the components of the dactyloscopic trace due to their high affinity (tendency to combine with each other) and color them gray to dark gray. The process is well suited for wet or damp tracks as well as for light and smooth surfaces. It is unsuitable for textiles. The track carrier is swiveled evenly in the mixture or, conversely, the mixture is kept in motion (circulation pump) until the track becomes visible. It can also be sprayed (use respiratory protection) or doused with the mixture. The securing of evidence is carried out photographically, after drying, additionally by removing the foil. The Manoxol molybdenum process is trace-friendly, but leads to considerable contamination of the trace carrier. It can also be used after the cyanoacrylate vapor deposition to increase contrast. A similar mixture is available on the market as "Aquaprint".

Ninhydrin

  • Ninhydrin: 2 g of ninhydrin are dissolved in 100 ml of ethanol . The solution is acidified with approx. 0.5 g of 20% acetic acid and then sprayed onto the fingerprint with a sprayer. To develop the impression, it is held over steam for a few minutes. Ninhydrin reacts with the amino acids and proteins in sweat and forms a purple compound with a complex structure.
  • NFN (Non Flammable Ninhydrin): The Non Flammable Ninhydrin solution causes a chemical reaction with some substances on the dactyloscopic trace. It works well with writing paper, newspapers, and cardboard; it is unsuitable for art print, glossy and photo paper. The trace carrier is immersed in the solution (the duration depends on the material thickness) or moistened with a cotton ball. After air drying, it is stored in the dark. The development of the traces takes 30 minutes to 72 hours; in urgent cases it can be accelerated by applying heat. Trace carriers treated with ninhydrin must immediately be placed in an airtight plastic cover, as touching them again would lead to further traces; In addition, harmful vapors or dusts can develop. Evidence is secured through photography.
  • NPB (ninhydrin petroleum benzine): The solution causes a chemical reaction with some components of the dactyloscopic trace. The harmful components of NFN ( trichlorotrifluoroethane and acetic acid ) have been replaced by petroleum benzine , but the resulting vapor mixture is explosive. Electrical systems and devices in the work area must be explosion-proof. NPB works well with writing paper, newspapers, and cardboard; however, it cannot be used with art paper, glossy paper and photo paper. The processing takes place in the same way as with NFN
  • Tetra-NPB (Tetra Ninhydrin Petroleum Benzine): The solution causes a chemical reaction with some components of the dactyloscopic trace. It is well suited for latent traces created by blood or blood water (the blood trace examination is not affected by the procedure). The mixture is poured into a jar until two layers have formed. The upper, light-colored liquid is poured off (must be disposed of), the lower, brown liquid is poured into the sprayer. The securing of evidence takes place in the original (with trace carrier) or photographically.
  • Ninhydrin - Acetone: The solution causes a chemical reaction with some components of the dactyloscopic trace. It works well for writing paper, newspapers and cardboard; it cannot be used for art print, glossy or photo paper. Acetone dissolves almost all font coloring agents, stamps, etc. The method may therefore only be used if the examination of these trace types can be dispensed with. The search for clues is carried out in the same way as with NFN
  • Onprint: Onprint (spray) is an industrial product that contains substances similar to NFN. It works well on writing paper, newspapers, and cardboard; it cannot be used on art paper, glossy paper and photo paper. The trace carrier is sprayed from a distance of 30 cm and air dried. When stored in the dark, the traces develop independently in a time of approx. 30 minutes to 72 hours.

Silver nitrate

Silver nitrate solution is well suited for looking for traces on absorbent surfaces, for utility paper; it is not suitable for art print, glossy and photo paper. The search for clues takes place in a darkened room. When treating the trace carrier, the typeface may have to be left out. The trace carrier is dipped into the solution, sprayed or dabbed and then dried (dark, if possible between two layers of blotting paper, better in a drying cabinet). One gram of silver nitrate (also Höllenstein, Latin: Lapis infernalis) is dissolved in 50 ml of methanol and applied to the trace carrier paper to be examined by means of an atomizer by lightly spraying. This is done on the trigger and with gloves. After drying with a hair dryer, the paper is irradiated with UV light (366 nm for approx. 2-3 minutes) until the fingerprints that are present are clearly visible. The fingerprints are visible as a purple, sometimes gray-black line pattern. First of all, silver ions from the sprayed-on solution react with chlorine ions contained in human sweat and thus in fingerprints. The sparingly soluble silver halide AgCl is formed. This decomposes under the action of light to free halogen and elemental silver. The silver nitrate solution can be kept closed. Alternatively, the remains of the solution can be left open in the fume cupboard and the remaining silver nitrate is disposed of as solid chemical waste. Over time, the entire trace carrier turns purple to gray-black.

Dry copier toner

Dry copy toner is a finely powdered coloring agent for electronic dry copy machines. It is used in the same way as carbon black powder. The dry copy toner can be fixed on the trace carrier by heating. Either a strong light source (like in a copier) or an open flame (carefully) is used for this. When securing with the track carrier, the track that has been made visible must be protected by a film.

Special procedures

High vacuum metal vapor deposition

With high vacuum metal vapor deposition , an existing trace on an object is made visible through a two-stage coating process. A coating with gold and zinc is typical, depending on the properties and color of the substrate, other materials can also be used (copper, aluminum, tin, silver, cadmium). The process requires a great deal of technical effort and is costly; it will therefore be considered in exceptional cases.

laser

The track can be recorded gently and without contact using laser light . Disturbing substrates, e.g. B. colors or patterns are eliminated. In contrast to traditional solid-state lasers, OPSL (optically pumped semiconductor laser) technology offers the possibility of making lasers available in any color in the visible spectral range. This opened the door to testing other wavelengths for their effectiveness in forensic science, especially in the visualization of hidden fingerprints. The result of these new possibilities are the commercially available lasers with a wavelength of 577 nm (yellow - Coherent TracER series) and in the deep blue spectral range (460 nm).

X-ray procedure

The track sprinkled with the finest lead powder is exposed to X-rays. The image can be viewed on an X-ray screen or fixed with a special film. Here, too, a great deal of technical effort is required. The method is suitable for trace carriers with a disturbing background (colors, patterns), with strongly curved surfaces, for inaccessible places (e.g. inside of vessels or pipes) and for traces on human skin.

Stereomicroscopy

The stereomicroscopy allowed because of the spatial impression of a better evaluation of the tracks, in particular of original tracks on the track support. This method is hardly suitable for searching for clues because of the narrow search field. The backup takes place photographically with the help of a microscope adapter. In stereomicroscopy, a lot of light is required in a very small space. Nevertheless, the object must not change due to the influence of heat. Cold light sources guarantee intensive lighting with "cold", i.e. infrared-free light. This visible light is transmitted directly to the object via high quality fiber optic light guides.

literature

  • Udo Amerkamp: Special methods of securing evidence - procedure for making dactyloscopic traces visible. Verlag für Polizeiwissenschaft, 2002, ISBN 3-935979-02-9 .
  • Brian Innes: Clues at the crime scene. Fingerprints, footprints and tire prints. Tosa, 2008, ISBN 978-3-85003-185-1 .
  • Peter Pfefferli: The trace: guide for tracing practice. 5th edition. Kriminalistik Verlag 2007, ISBN 978-3-7832-0031-7 .

Web links

Individual evidence

  1. ↑ Nadine Hege: The classical and the genetic fingerprint. 2006. (www.benecke.com ( Memento from July 23, 2011 in the Internet Archive ) accessed on January 1, 2010)
  2. ↑ H. Horch: Argentorat. In: Archives for criminology (criminal anthropology and crime statistics). Volume 92-93, FCW Vogel, Berlin 1933.
  3. ↑ a b c Udo Amerkamp: Special methods of securing evidence. Process for the visualization of dactyloscopic traces. Verlag für Polizeiwissenschaft, 2002, ISBN 3-935979-02-9 .
  4. ↑ Attestor Forensics. Newsletter, PolyCyano, http://www.attestor-forensics.com/
  5. ↑ a b H. J. Bader, M. Rothweil: Forensic chemistry - investigation of crimes with chemical methods. In: CHEMKON. Volume 10, No. 4, 2003, pp. 181-186.
  6. ↑ Heribert Freimuth: Latent fingerprints on adhesive tapes. In: Criminology. 11/2001, p. 737.
  7. ↑ Sticky-Side Powder. (www.redwop.com ( Memento from July 15, 2011 in the Internet Archive ) accessed on January 1, 2010)
  8. ↑ a b c H. H. Huelke: Forensics , securing and exploiting crime scene traces. Heidelberg / Hamburg 1977, ISBN 3-7832-0376-7 .
  9. ↑ Fluorescent powders for developing latent fingerprints with forensic light sources / lasers. (www.krimtech.de , accessed December 31, 2009)
  10. ↑ Attestor Forensics. Newsletter. Anti-Stokes Viewer, http://www.attestor-forensics.com/
  11. ↑ SJ Gardner, DF Hewlett: Optimization and initial evaluation of 1,2-indandione as a reagent for fingerprint detection . In: Journal of Forensic Sciences . tape 48 , no. 6 , November 2003, p. 1288-1992 .
  12. ^ Karl König In: Archive for Criminology (criminal anthropology and crime statistics). Volume 39-40, FCW Vogel, Berlin 1910.
  13. ↑ Voigtländer Police and Forensic Technology. Product description, 1998.
  14. ↑ Hammer: About methods for displaying latent fingerprints on human skin. In: Forensic Science International. Volume 16, No. 1, July-August 1980, pp. 35-41.
  15. ^ Chemical Institute of the University of Heidelberg: Chemical reports. Volume 89, Verlag VCH Verlagsgesellschaft, 1956.
  16. ↑ Bischoff: About the use of Barlappesamen for securing evidence. In: Journal of Applied Chemistry. Part 1, Verlag Chemie, 1911.
  17. ↑ Heike ME Andree: Death Detectives - on the trail of death: An introduction to forensic science. BoD - Books on Demand, 2007, ISBN 978-3-8334-7072-1 .
  18. ^ Weihmann: Kriminalistik: For study and practice. 10th edition. Publisher German Police Literature, 2008.
  19. ^ Walter R. Scott: Fingerprint mechanics: a handbook; fingerprints from crime scene to courtroom. Thomas, London 1951.
  20. ↑ Othmar Georg Koch, Gertrud A. Koch-Dedic: Handbook of trace analysis. Springer, Hamburg 1964.
  21. ↑ fingerprints. (www.cumschmidt.de , accessed December 31, 2009)
  22. ^ A b c d Henry C. Lee, Robert E. Gaensslen: Advances in fingerprint technology. CRC Press, 2001.
  23. ↑ G. Kaiser: Kriminologie. An introduction to the basics. 10th, completely revised edition. Heidelberg 1997.
  24. ^ Chlorides in inks
  25. ↑ Lipscher: Chemistry and Crime. In: Chemistry in Our Time. Volume 32, 1998, pp. 143-149.
  26. ^ Rijksuniversiteit te Leiden, Abstracts on police science , Volume 2, Kluwer BV, 1974.
  27. ↑ TracER - Compact Forensic Laser System. (www.coherent.com ( Memento from September 20, 2010 in the Internet Archive ) accessed on January 1, 2010)