Although often used as a collective term, being placed "under arrest" is a specific legal situation where an individual is no longer legally able to walk away from law enforcement, which often is well before being processed into incarceration. To make an arrest, law enforcement must have probable cause determining that you have committed a crime, which allows them to take you into their custody. Sometimes, a person can be charged with a crime and not placed under arrest, which is termed a citation. Common citations include traffic offenses among other items. Even if an arrest is determined lacking in probable cause later, persons in custody cannot resist the arresting officer, nor are they guaranteed absolution from charges stemming from the initially illegal arrest.
An arrest warrant is an official document approved by a judge or magistrate, which authorizes law enforcement to take a given person into custody. In most cases, the arrest warrant must contain the suspect's name, the crimes they stand accused of, and other restrictions on where and how this suspect can be detained.
For law enforcement to obtain an arrest warrant, they must present evidence under oath or affidavit to a judge or magistrate that clearly states a crime occurred and the person mentioned in the arrest warrant was in some way responsible for this crime. In the arrest warrant, certain details and information connecting the person being arrested to the crimes in question must be made available to both the issuing court official, as well as the suspect at the time of their arrest.
Typically, there are only two circumstances where an officer can make a warrantless arrest, which include:
Other situations, known as "exigent circumstances" allow an officer to make an arrest if they believe a suspect to be an immediate threat to themselves, the officer, or other civilians. Also, if an officer is in active pursuit of a suspect, warrantless entry and warrantless arrests can occur until the pursuit and factors surrounding the pursuit are determined.
First, an officer apprehending a suspect typically must follow a procedure known as "knock and notice", which makes police announce their presence, give occupants time to come to the door, and prevents law enforcement from barging into your home unnecessarily. However, "knock and notice" procedures can be ignored for different reasons, including:
The amount of force an officer is allowed to legally use during an arrest is generally determined by the amount of resistance a suspect offers. The courts determine if force used was "excessive" or "use of unnecessary force". However, depending on the situation, an officer has several non-lethal and lethal choices to protect him or herself and complete an arrest. Generally, law enforcement can only use lethal force if a suspect points a weapon at officers, is about to commit a violent felony, or threatens the safety of third parties. For many cases, being in a car chase immediately endangers the safety of officers and third parties; therefore, use of lethal force is permissible.
Your best bet is to not. Realistically though, almost every state provides citizens the right to make an arrest if they personally see the commission of a crime, or have probable cause to believe a suspect committed a felony. However, detaining your "suspect" might actually be considered false imprisonment or even kidnapping if you violate someone's legal rights in the process. That is just the criminal liability you may endure. In addition, there is the question of civil liability you may incur from detaining your "suspect". Some states, however, have specific laws allowing individuals to protect their "domain" or home and property with lethal force. In addition, if any individual threatens your safety, you can use lethal force to prevent this from happening. Making a citizen's arrest of a person that threatened your safety would be hard to prove however, if you managed to gain full control and custody of that person. Typically, the courts look extremely harshly at citizen arrests and are not too thrilled about individuals actively exercising these rights.