1. The officer’s observation of the evidence must be lawful, meaning the officer had a legal right to be at the location, or the suspect did not have a reasonable expectation of privacy in the location,
2. The officer must have a lawful right of access to the object, and
3. The officer must have probable cause to believe the object is evidence of a crime.
Plain smell falls under the “probable cause” prong of the plain view rule and would be considered circumstantial evidence, as determining the existence of something based on smell can only be inferred until the actual the object is seen and verified. Plain smell may also fall under the doctrine of exigent circumstances if there is an urgent need for an officer to take action based on the totality of the circumstances surrounding the suspect odor. (People v. Duncan (1986) 42 Cal.3d 91, 103). In this case, the officer must believe the threat would have materialized before a warrant could be obtained. For example, a Meth lab or PCP lab might be considered exigent circumstances, as the chemicals used in the production of those substances are highly volatile and could explode. An officer relying on plain smell as probable cause should always attempt to obtain other