United States v. Watson
Most juridictions allow arrest for a felony without a warrant as long as probable cause for the arrest can be articulated.
Without a warrant you must find reasonable grounds to arrest someone, whereas with a warrant your reason to arrest the suspect already exists. Without a warrant a Police Officer can arrest anyone without permission of a Magistrate as long as they follow the correct procedures so their arrest is lawful, which is unlike an arrest with a warrant where you must be granted the warrant to be able to arrest that person. Without a warrant, a Police Officer can mess the arrest up and make it an unlawful arrest but with a warrant it is very unlikely that they make it an unlawful arrest.
probable cause
Probable cause is determined by a statement of the facts in a case, including how much evidence the police have to prove their case. Probable cause is the determination that it is likelier than not a person has committed a crime or is committing a crime. There are different levels of probable cause, including for search warrant and for an arrest warrant. A probable cause for a search warrant isn't necessarily a probable cause for an arrest, and vice versa
A police officer must have probable cause in order to arrest someone. They can arrest a person if they see a crime taking place or if an arrest warrant has been issued.
judge
Yes, police can arrest you at your workplace if they have a warrant or probable cause to do so.
Probable cause or a warrant.
Probable cause or warrant
When he has probable cause to believe that the person he is arresting has committed, or is about to commit, a criminal offense.
In California an arrest for a misdemeanor can be made without a warrant IF the offense was committed in the presence of the officer/citizen making the arrest ( see penal code section 836 & 837. Arrests can also be made for a felony without a warrant IF a felony has in fact been committed and you have probable cause/reason to believe the person committed the felony.
Until he has sufficient probable cause to sustain a warrant for an arrest.