Whats the main differences between arrest with and without a warrant?

Answer 1

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.

Answer 2

A so-called "regular" arrest (known as a 'summary arrest') usually occurs immediately upon, or soon after, the commission of the offense. Such an arrest is made when the arresting officer(s) has observed the crime/violation or have "probable cause to believe" that the arrestee is the one who committed it. A 'warrant' arrest is usually made after some time has passed, or the results of an investigation have established that "probable cause" has been developed that the person named in the warrant is the perpetrator. When an arrest warrant has been issued it is NOT necessary that the arresting officer have it in his possession. Merely knowing that the warrant exists and is 'active,' is sufficient to make the arrest if the perpetrator is encountered.

Answer 3

The main difference would be that to obtain a warrant, probable cause would have to be presented to a judge; there would be evidence and/or testimony to support the warrant. An arrest without a warrant would be one that someone, usually an officer, caught someone in the act of committing the crime.