Final answer:
Law enforcement can seize evidence without a warrant in situations of exigent circumstances, with consent, if the evidence is in plain view, when searching a vehicle, or at international borders. The exclusionary rule prohibits the use of illegally obtained evidence, with certain exceptions like good faith or inevitable discovery. No-knock warrants have recently been limited.
Step-by-step explanation:
Law enforcement can seize criminal evidence without a search warrant under certain circumstances. The Fourth Amendment protects against unreasonable searches and seizures, typically requiring a judge to issue a search warrant based on probable cause.
However, there are exceptions to this requirement. One key exception is when there is exigent circumstances, meaning that there is a reasonable expectation that evidence may be destroyed or tampered with before a warrant can be obtained. Additionally, if the owner or renter consents to the search, or if the items in question are in plain view, a warrant is not necessary.
The exclusionary rule prevents evidence obtained through an illegal search or seizure from being used at trial. However, this has exceptions as well, such as the 'good faith' exception, where officers believed they were acting on a valid warrant, and the 'inevitable discovery' doctrine, where the evidence would have been found regardless of the illegality.
Other situations where a warrant is not needed include searching the passenger compartment of a vehicle or searching individuals entering the United States. When a warrant is needed, officers must show probable cause but not enough evidence for a conviction. For example, no-knock warrants have recently faced scrutiny and limitations.