Because our Constitution does not allow unreasonable searches, one might think that a search warrant is always required to search someone's home or vehicle, but over the years courts and legislatures have carved many exceptions to the general rule.
There are specific factual situations when a law enforcement officer does not need a Search Warrant despite the Constitution’s requirements.
Law enforcement officers are under no requirment to be honest with a citizen and part of effective police tactics often entails giving an individual a false impression of the legal status of a particular search. A judge will not throw out a case based on mere misrepresentation by law enforcement unless it is egregious or outrageous.
Many years ago while I was a green prosecutor in Clearwater, Pinellas County, Florida, fresh and newly mented out of law school, a friendly officer who was fairly new to Florida but had earlier been a cop in New Jersey for a number of years, laughingly told me about a Defendant who was so verbally abusive upon arrest for something trivial that he wished he'd had a "throw bag."
"Throw bag?" I asked (when I said I was green, I meant it).
He looked at me in disbelief that anyone could be so naive, "A bag of pot, coke, meth for troublemakers that shows up when I make a difficult arrest."
So it appears there’s a fifth exception to the Constitutional requirements of a Search Warrant to gather evidence never taught in American Law Schools where there is no evidence at all - not until law enforcement arrives with a throw bag or two.