What is required for a defendant's arrest to be legally justified?

For a defendant's arrest to be legally justified, it is essential that probable cause is established. Probable cause refers to the reasonable belief, based on facts or circumstances, that a crime has been or will be committed by the individual in question. This standard is a fundamental principle in the criminal justice system that protects individuals from unwarranted arrests and ensures that law enforcement officers have sufficient grounds to take someone into custody.

The requirement for probable cause serves as a safeguard against arbitrary actions by police officers, ensuring that arrests are made based on evidence or reasonable suspicion rather than mere speculation or bias. This legal threshold must be met before an officer can seize an individual and is crucial for the integrity of the legal process.

The other choices do not suffice as justifications for an arrest. Personal knowledge of the crime by the officer, while it may contribute to establishing probable cause, is not an independent requirement; it's the overall context and evidence that creates the necessary probable cause. Authorization from the District Attorney is not required for an arrest; officers can make arrests based on their own determinations of probable cause. Lastly, witness statements might aid in establishing probable cause, but they are not a standalone requirement. Probable cause remains the cornerstone of lawful arrests.