Final answer:
Richard Quinney's Marxist proposition for understanding crime is that law is a tool of the ruling class.
Step-by-step explanation:
Among the Marxist propositions for understanding crime as set forth by Richard Quinney is the statement that law is a tool of the ruling class. This is aligned with the conflict theory perspective, which views social and economic factors as causes of crime and considers that laws may be designed to maintain and expand the positions of power of the ruling class. This perspective contrasts with other theories of crime that might, for example, focus on crime as a rational choice or the result of biological or psychological factors.