While it is a decision for your local courts, most will allow a search without a warrant if probable cause can be clearly articulated.
Since the car can easily leave the city, county or state where the officer is employed, exigent circumstances are almost automatic.
If he has probable cause of a crime then he may search without a warrant.
They can search your car without a warrant if they have "probable Cause".
Additional: For an officer's safety the law does permit the officer to visually observe AND do a cursory 'check' of the areas in which the driver (and any passengers in the vehicle) are seated and which are within their reach.
An officer would not need a warrant if probable cause exists.
Officers can often search vehicles after a lawful stop because one has "a lesser expectation of privacy in a motor vehicle as its function is transportation and it seldom serves as one's residence or the repository of personal effect." (Scarry, 2008, p.62)
This is also known as the automobile exception. Warrantless searches are often justified because of a vehicle's mobility, that is, a vehicle can be easily moved. This would especially cause problems if it is moved out of the jurisdiction.
The precedent for a warrantless search of an automobile was established in Carrol v. United States.
Source - Hess, Karen, and Christine Hess Orthman. Criminal Investigation. Clifton Park, NY: Delmar, 2010
In the U.S. technically, no they can't legally unless you give them permission.
A police officer may not enter your property without exigent circumstances. That being said, if the officer has probable cause or exigent circumstances to enter your property, you must allow them.
One example would be exigent circumstances, such as: An officer is dispatched to a report of a loud argument at a certain house. He arrives and hears screams coming from inside the house. He looks through the window and sees one person assaulting another. The police officer now has probable cause to believe that immediate entry into the house is necessary because someone inside the house is being hurt. There are many other examples, but the all boil down to one of the following: 1. Consent 2. Exigent circumstances 3. Plain view 4. Incident to arrest 5. When in "hot pursuit" of a fleeing criminal.
(1) Fresh Pursuit, or (2) Exigent circumstances.
One example would be exigent circumstances, such as: An officer is dispatched to a report of a loud argument at a certain house. He arrives and hears screams coming from inside the house. He looks through the window and sees one person assaulting another. The police officer now has probable cause to believe that immediate entry into the house is necessary because someone inside the house is being hurt. There are many other examples, but the all boil down to one of the following: 1. Consent 2. Exigent circumstances 3. Plain view 4. Incident to arrest 5. When in "hot pursuit" of a fleeing criminal.
It depends on the circumstance. A police officer cannot randomly search a person for no reason; however, there are many situations in which an officer can search without a warrant. Among those is probable cause and exigent (or emergency) circumstances. An officer, also, has the ability to do an outer-clothing patdown if they have reasonable suspicion that an individual is armed (Terry v. Ohio, Terry Stop, or Stop and Frisk). An officer, also, has the ability to conduct a search of the suspect after an arrest has been made (Search Incident to Lawful Arrest).
Under no circumstances can a police officer stop you or search you without probable cause. Probable cause is one of the ways that an ordinary citizen's right to privacy is protected from unlawful search and seizure.
You have the right to refuse a search of your car unless the officer has a valid search warrant or probable cause to believe there is evidence of a crime in your vehicle. However, it's important to comply with the officer's instructions to avoid escalating the situation.
It is assigned to an officer/detective to investigate who will look into the circumstances of the offense and determine who it was that did (if they are unknown) and if there is sufficient probable cause to arrest the individual.
Many small things can be combined to create probable cause. Most often PC for a search warrant comes from either the criminal investigation of a crime in which you are suspected of being involved, or from a named or confidential informant. Searches without a warrant are usually exigent circumstance searches in which the officer can articulate a specific need to search without a warrant. Most often this is used in searching a car. Because a car is mobile and easily hidden, an officer may feel that he has probable cause to search because (for example), through his training and experience, he detects an odor of marijuana. The exigent circumstance exists because if he releases the car and waits to obtain a search warrant, the evidence will probably be gone.
The severity of the crime at issue. Whether the suspect posed an immediate threat to the safety of the officer or others. Whether he was actively resisting arrest or attempting to evade arrest by flight. Any other exigent circumstances that existed at the time of arrest.
If probable cause is given then yes, the officer can.
"Probable Cause" is the foundatiion on which all arrests are based. It is a reasonable belief that a person has committed a crime. The test for whether probable cause exists for the purpose of an arrest is whether facts and circumstances within the officer's knowledge are sufficient to warrant a prudent person to believe a suspect has committed, is committing, or is about to commit a crime. See: http://www.lectlaw.com/def2/p089.htm