Can law enforcement officers arrest me without a warrant if I am at a friend’s house?

According to the laws governing warrant requirements, law enforcement officers can make an arrest without a warrant if you are at a friend's house or in another person's home under certain circumstances, if there is an exception to the warrant requirement. The exceptions to the warrant requirements vary by state.

Can law enforcement officers arrest me without a warrant if I am at a friend’s house?  

An arrest is considered a “seizure” of your person under the Fourth Amendment of the U.S. Constitution. In order for a judge to find your arrest to be illegal, the law enforcement officer's actions must have been unreasonable.

If you are in another person's house, the applicable exceptions to the warrant requirements are plain view or exigent circumstance. Exigent circumstances are also sometimes called emergency circumstances. If law enforcement officers are lawfully present in a house, they may seize contraband objects and persons holding contraband objects which are in plain view.

In an example scenario, a police officer comes to the door because of a noise complaint. He asks to come in, and your friend gives consent. If the officer sees you with a spoon of heroin, he has probable cause to arrest you without a warrant. You are holding an item that is illegal. There are valid grounds to charge you with the possession of an illegal drug and an item of drug paraphernalia.

Do exigent circumstances allow law enforcement offers to forego warrant requirements?  

Exigent circumstance covers situations in which law enforcement officers have reasonable cause to believe that there is an urgent need to protect the lives and property of individuals. Say you are committing an armed robbery. The police see you committing the act. You drive away from them, causing a dangerous high-speed chase. Then you enter your friend's house. Law enforcement officers can lawfully come into the house and take you into custody. The situation is considered an emergency.

Warrant requirements allow law enforcement officers to legally enter a house and arrest a person if they obtain consent from a resident of the house, if the contraband is in plain view, or if there is an exigent circumstance. If the law enforcement officers did not have a lawful reason to enter your friend's house, you can move to suppress any incriminating evidence that they recovered.