To determine case of thief either laid out over with a large quantity of possible theft-suspicious an author, or in order at a place, where already repeats thefts were committed, the thief or the thieves to seize. As proof chemical substances are laid on on the object which can be secured, those by the author, whose clothes or other articles are accepted and later to be chemically proven to be able. As chemicals substances on organic basis (Ninhydrin) are used, Rhodamin B, phenolphthalein) and inorganic basis (silver nitrate). If a theft is to be cleared up by gasoline, Diesel or fuel oil, an indicator is added to the liquids, which is originally not contained in these products.