Final answer:
If abandoned property is the result of unlawful police activity, it cannot be used as evidence due to the exclusionary rule. However, there are exceptions where police can search and seize property without a warrant and legally use it as evidence.
Step-by-step explanation:
The scenario where police are not allowed to use property as evidence even if it is abandoned pertains to the legality and admissibility of evidence in criminal proceedings. Evidence found as a result of unlawful police activity, such as conducting an illegal search or seizure without a warrant, is generally inadmissible in court under the exclusionary rule, established by landmark cases such as Mapp v. Ohio. This means that, if the abandonment of the property is the result of unlawful police activity, it cannot be used as evidence.
However, there are exceptions to the warrant requirement in cases where a person lacks a "reasonable expectation of privacy," or the property is in plain view, exigent circumstances are present, or if there is consent given for the search. These exceptions indicate times when the police may conduct a search or seize items without a warrant but still use the discovered property as evidence.