This criminological study on police experiences, attitudes and decisio
n-making in the field of drug-related crimes includes participant obse
rvation, questionnaire studies among drug investigators (n = 465) and
police officers working in other fields of investigations (n = 259), a
nd interviews with experts at all levels of police organization and in
different regions (n = 78). Contrary to the fundamental 'principle of
legality' of German law, in the field of drug-related crime, police d
iscretion is de facto almost as wide as in legal systems following a '
principle of expediency'. The police itself decides whether to initiat
e criminal procedures mainly against users or against dealers; decisio
n-making depends on individual and regional valuation of drugs and dru
g prohibition as well as on expectations of politicians, authorities,
and the general public. In criminal cases of drug abuse the police act
ually is 'master of preliminary investigations' even though in Germany
this function by law is assigned to the prosecuting attorney. Due to
the methods of undercover investigations, part of the prosecuted crimi
nality appears to be 'constructed' by the state.