An Exchange in Locard’s Own Words (Part 3)

Translated by Kathleen Brahney
Commissioned by McCrone Associates, Inc.

Edmond Locard
Doctor of Medicine, Professor of Law, Director of the Lyon Laboratory of Police Techniques,
Vice-President of the International Academy of Criminology

Manual of Police Techniques
Third Edition, Completely Revised and Augmented.
Paris: Payot, 16 Boulevard St. Germain, 1939

Part III—Dust Traces

Chapter III, Traces


Dust taken from the clothing of an individual can indicate what the person was doing prior to the crime.  Dust from various parts of clothing or the body can be put to useful analysis.

  1. CLOTHING: Place the clothing that is to be examined in a big paper bag and beat the bag for about five minutes with a flexible rod.  One then gathers the dust from the bottom of the bag.  One then separates out the debris that has an appreciable volume and which can be examined individually.  The rest is examined under a microscope at a low level of enlargement.  It is preferable to use Soderman’s large instrument, with an electrolux (sic) adapter [illuminator?].  It is impossible to give a complete plan for the analysis because of the great variety of cases.  One will note only the following points (for a complete study of dust, see The Treatise on Criminalistics, Vol. II:
    1. Dust from various professions:  This would be the debris left by certain professions – plaster, chalk, sawdust, dust from dried glue in the case of a carpenter; dust from plants in the case of an apothecary, etc.  One can then determine the profession of the person who has left clothing at the scene of a crime.
    2. Metallic Dust:  A counterfeiter might have enough metallic dust on his work clothes to allow one to determine qualitatively and, to some extent quantitatively, the alloys he has been using.
    3. Organic Debris.  Except for traces of blood, which undergo their own special methods  of examination, one may encounter dried animal and plant material that can be identified.  A murderer was once identified through the presence of the winged seed of a salsify plant attached to his sleeve, which was from the tuft of a plant found next to the scene of the crime. 
  2. SHOES: If an examination is made immediately following the crime, or if the shoes have not been worn since the crime, dried mud can indicate the path taken by the criminal (flour from a mill, wool from a rug, dirt from the ground, etc.  Dust from trouser legs can yield the same kind of information.
  3. POCKETS: Pockets should be turned inside out and brushed.  Dust can indicate the items the pocket has contained – sealing wax in the case of stolen registered letters, candle wax from a robbery, crumbs from stolen food items, etc.
  4. WEAPONS: Dust may be found in the chips and grooves of knife-blades, in the sheaths of daggers and swords; this dust might indicate the use to which the weapon was put (ruling out blood traces); these uses might include fibers from plants if the blade was used in cutting down a field, debris from grasses for a sword dried off with grass, etc.
  5.  FINGERNAILS: In each arrest, the fingernails of the detainee should be cleaned.  One might find blood, organic debris (in the case of rape, sexual crimes, murders and dismemberments), or dust or powder characterizing a stolen object (chocolate, butter, cloth), or dust indicating the path taken in committing the crime (plaster, cable or rope grease, etc.)

  6. SKIN RESIDUES: Dust taken from the skin almost always is found in the form of grime or filth. In addition to dust associated with a profession, one should note tobacco traces on the fingers of smokers and traces of powder.  Movements made by the naked torso in certain professions will provide dust in the hairy parts (the front of the thorax or the armpits), and in the cutaneous folds (under the collarbone or in the navel).

  7.  HAIR: One encounters dust from professions and road dust.  This dust can be gathered by rinsing the hair with alcohol and then letting the alcohol evaporate.

  8. EAR WAX: Severin Icard, in collaboration with Jean Maurel, has studied dust that has been incorporated into ear wax (Nature, No. 2457, May 7, 1921).  Any person who has spent a long time in a dusty environment carries an imprint of that environment in his outer ear canal.  The presence of ear wax is a constant, even after meticulous personal grooming.In the case of a day laborer who had worked several months on the docks unloading coal, Icard found traces of carbon dust in the worker’s ear wax, even though the worker had had no contact with coal for more than a year.  It is the same for roasted coffee, bits of hair (in the case of a hairdresser) or dust from flour (in the case of a baker).Naturally, one should not attach great importance to a few bits of common dust.  For the presence of a common substance to allow for general conclusions, one must find an abundance of the substance in question. Thus, Icard found various kinds of plant dust in the case of grain workers and winnowers, dockworkers (those who would be unloading peanuts, wheat or grains), sawyers, workers in factories that process plant material. If the substance is rare, however, even a small, definable quantity can be revealing (dust from copper, aluminum, mother-of pearl, sulfur, bauxite, glass, etc.).The technique to be used is as follows:  Using an ear tool, take out a certain quantity of ear wax and smear it onto a slide.  One should make two batches.  For the first batch, spread a bit of ear wax on a glass plate; cover with another plate, then with a second plate, and press.  The wax will spread out and is then examined at a weak level of enlargement (60–90 diameters), then if necessary, at a stronger enlargement.  One will then be able to distinguish if there are one or several kinds of foreign bodies in the wax.Black traces:  carbon, metals (iron, copper, aluminum, etc.)  Carbon will present sharp points, whereas iron, aluminum and above all, copper, will present irregular, uneven edges.

    Grayish traces:  mineral dust (limestone, chalk, cement, plaster, etc.).

    Transparent matter:  Most often, these are various kinds of crystals, dust from vegetable matter (debris from leaves, fibers, seeds, cotton, linen, flax, etc.) or dust of animal origin (silk, wool, hair, feathers, etc.).

    The fatty matter in earwax is not a hindrance in chemical reactions.  By mixing the earwax with a drop of iodine/potassium iodide (.570 iodine in a one-fiftieth solution of KI) the grains of free starch will turn violet.  In order to color the cellulose of vegetable fibers and starch grains included in these fibers the same purple, one would use zinc chloride in a concentrated solution of iodine/potassium iodide.

    The second batch is calcined (i.e., heated to a high temperature to drive off volatile substances) and the components in the residue will be examined using normal chemical procedures or microscopic examination.  This second examination is primarily focused on identifying metallic powders (iron, copper, lead oxide salts, aluminum, etc.) and minerals (chalk, cement, plaster, etc.).

Editor’s Note

Locard follows on with techniques for the identification of many of these dust traces in his Chapter IV.  Watch for Parts IV, V and VI of this exchange.


Edmond Locard, Treatise on Criminalistics.

Hans Gross, Handbuch fur Unterschungsricher, Munich, Schweitzer, 1908; the same has been translated into French, ­translated by Bourcart and Wintzweiller, Paris, Marchal and Billard, 1899.

R.A. Reiss, Manual of Scientific Policing, Lausanne, Payot, 1911.

Lacassagne and Etienne Martin, Summary of Legal Medicine, Paris, Masson, 1921.

Edmond Locard, Criminal Investigation and the Scientific Method, Paris, Flammarion (n.d.)

Tomellini, Manuale di polizia giudiriazia, Milan, Heopli, 1912.

Marcelle Lambert and Balthazard, Human and Animal Hair, Paris, Steinheil, 1910.

Nicolae Minovici, Manual Technic de Medicina Legala, Bucharest, Socecu, 1904.

H. Coutagne and Florence, “Fingerprints and Judicial Expertise,” Archives of Lacassagne, No. 19, 1889.

Andre Frecon, Fingerprints in General, Lyon, Storck, 1889.

E. Godefroy, Elementary Manual of Police Techniques, Brussels, Larcier, 1932.

Charles Manget, Synoptic Tables for the Analysis of Tissues and Textile Fibers, Paris, J.-B. Bailliere, 1902.

George Bertillon, Anthropomorphic Reconstruction Using Clothing Measurements, Paris Thesis, 1892.

Ainsworth Mitchell, “Circumstantial Evidence from Hairs and Fibers,” The Internal Review of Criminalistics, No. 1, July, 1929.

M. Chavigny, “Vehicle Traces,” The Internal Review of Criminalistics,­ No. 1, July, 1929.

Harry Soderman and Ernst Fontell, Handbok I Kriminaltecknik, Stockholm, Wahlstrom and Widstrand, 1930.

F. Louwage, Techniques in Thefts, Brussels, 1922.

John Glaister, A Study of Hairs and Wools, Cairo, Misr Press, 1931.

Popp, Die Mikroskopie im Deinst des Kriminaluntersuchung, in Arch. De Gross, 70 BD., 1918.

George Vuillemin, Dust from the Medico-Legal Point of View, Nancy Thesis, 1926.


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