A more thorough explanation:

Plain view doctrine is a rule that allows police officers to seize evidence of a crime without a warrant when the evidence is clearly visible. This means that if an officer sees something illegal in plain sight, they can take it as evidence. It is an exception to the Fourth Amendment's right to be free from searches without a warrant.

For the plain view doctrine to apply, the officer must have a lawful right to access or observe the seized object. This means that if the officer violated any laws in arriving at the location or situation where they had access or sight to the object, then the plain view doctrine does not apply.

One example of the plain view doctrine is the case of Horton v. California. In this case, the officer had a warrant to enter a robber's home and seize property stolen through an armed robbery. The officer did not find the stolen goods but found the weapons that he suspected the robber used in the robbery in plain sight, and properly seized them under the plain view doctrine even though he did not have a warrant for the weapons.

Another example is the case of INS v. Delgado. Immigration enforcement officers entered a factory pursuant to consent and had consent-based encounters with the employees, which meant that they lawfully situated themselves. While there, they saw evidence of illegal activity in plain view and were able to seize it under the plain view doctrine.

Overall, the plain view doctrine allows officers to seize evidence without a warrant if it is in plain sight and they have a lawful right to access or observe it.