Searches are a standard part of police investigative work, and sometimes they need a warrant. Other times they do not.
However, when the police obtain evidence in an illegal search and seizure, it should not be admissible.
When a search is legal
Anytime the police receive a warrant to conduct a search, they can legally access the property. The warrant provides them with legal entry and protects citizens from unreasonable searches and seizures. This is your Fourth Amendment right according to the Constitution. For a warrant to be valid, the officers must request it in good faith, have trustworthy information to prove the need for it, and specifically state the items they need to find and where they intend to look.
When police do not need a warrant
Under certain, well-defined circumstances, police do not need a warrant to conduct a search. For example, they may conduct a warrantless search if they can prove probable cause or if they believe the suspect to be a flight risk. If you give consent, they can search your property. However, they must stop if you withdraw consent or provide them with a time limit.
Knock and announce in Florida
Florida has a Knock and Announce Statute that states police offer must provide due notice of their reason for conducting a search before entering the property. In practice, this means they cannot simply burst into your property without explaining why they are there and giving you a reasonable amount of time to respond.
Every situation has unique circumstances that can affect the case.