By Robert Phillips  
Deputy District Attorney (Ret).

• Attempted detentions 
• Flight and probable cause to arrest 

United States v. Hamilton (9th Cir. Mar. 24, 2025) 131 F.4th 1087 

Rule: An attempted, but unsuccessful, detention, does not implicate the Fourth Amendment. Probable cause justifying a warrantless arrest exists where, under the totality of the facts and circumstances known to the arresting officer, a prudent person would have concluded that there was a fair probability that the suspect had committed a crime. Flight from law enforcement can be suggestive of wrongdoing and give rise to probable cause to arrest when coupled with preexisting specific reasons to suspect that the person fleeing may have engaged in criminal conduct. 

Facts: Around 2 a.m. on Feb. 14, 2021, officers from the San Francisco Police Department responded to reports of a shooting in the Tenderloin District. Police found three shooting victims. The decision doesn’t tell us, but apparently the resulting injuries were not life-threatening. The victims all described a “small Black man” as the shooter. The victims also told investigators that they observed the suspect having an altercation with a woman who had arrived at the scene in a taxi, after which the suspect forced her into a black Hyundai. All of this was also ....