Method for identifying of a biological sample of a mammal, composition for use in this method and kit for performance of this method

A method for identifying a biological sample of a mammal, the method comprising:

• administering to the mammal a capsule comprising a capsule composition and a capsule outer shell, wherein the capsule composition comprising at least two essentially non -metabolizable marker substances and a dye, wherein the capsule composition administered to the mammal comprises an amount of the dye effective to color oral mucosa of the mammal, the at least two essentially nonmetabolizable marker substances comprise a plurality of polyethylene glycols (PEGs) with different molecular weight relative to each other, wherein the molecular weight of each of the plurality of polyethylene glycols is less than 5000 kDa;
• the capsule outer shell preventing contact between the dye and the oral mucosa of the mammal;
• if the capsule is chewed, the capsule outer shell allowing contact between the dye and the oral mucosa of the mammal;
• collecting a biological sample from the mammal;
• examining the biological sample for the presence and/or amount of the at least two essentially non-metabolizable marker substances and optionally of the dye;
• and
• examining the biological sample for at least one specified analyte selected from the group consisting of illegal drugs, a barbiturate, a barbiturate derivative, nicotine, alcohol, a doping agent and combinations thereof.