All arrests begin with an encounter with law enforcement, but not all encounters with Law enforcement should end in an arrest without initial probable cause. In a recently decided California Appellate Case [People v. Linn (1st App.Dist. Div.Two 2015) A145052] the Court examined the question as to whether a voluntary encounter with law enforcement rises to the level of a detention. The Fourth Amendment of the United States Constitution guarantees freedom from unreasonable searches and seizures and requires such searches and seizures to be preceded by warrants supported by probable cause or, in the absence of a warrant, sufficient probable cause on the part of law enforcement to detain and search suspects.

The Appellate Court held that even if an officer engages someone in a consensual exchange, even if the officer is speaking to that person in friendly non-commanding manner, if that that person being engaged reasonably feels that they are not allowed to leave or otherwise end the encounter, then the officer must have probably cause to initiate the exchange This was illustrated by the facts discussed by the Court.

The Linn case began when a motorcycle officer observed passenger of a SUV flicking ashes out of the passenger window. While the officer could have initiated a traffic stop and issue a traffic code violation, he did not do so, but, instead, followed vehicle until it parked and pulled next to driver's side door. When Nicole Linn, the driver, exited vehicle holding a cigarette and a soda, the officer engaged her by asking questions about the passenger flicking ashes out the window. While they were talking the officer told Ms. Linn to put down both her cigarette and her soda. Ms. Linn voluntarily showed her driver's license to the officer, which he took and proceeded to conduct a background check on her record. The officer then walked over to the passenger and began to ask questions, fill out a report on a clipboard, and do so while retaining possession of Ms. Linn's driver's license. At that point the officer smelled alcohol on Ms. Linn's breath and determined that she had been driving while under the influence and arrested her for DUI.

The Appellate Court stressed that they were not going to specify a bright-line rule regarding the officer taking and examining a voluntarily offered id card. Despite that exception, however, in this like all 4th Amendment cases the Court considered the totality of the circumstances leading up to the arrest of Ms. Linn. In those circumstances leading up to her arrest, the Court determined that a reasonable person in Ms. Linn's position would have believed that they were not permitted to leave based on the facts of the case, which means that the officer must have probably cause before initiating an encounter that leads to an arrest. In this case, the officer asked Ms. Linn about her passenger's act as if the officer believed that Ms. Linn held some legal responsibility for the act of her passenger, told Ms. Linn not to leave when she tried to do so, told her to put her soda and cigarette down, performed a background check on driver without explanation after she have offered to show it to him, and held onto her driver's license while he took a report from the passenger. The Court concluded that, "[i]n short, an objectively reasonable person would not have felt free to end the encounter with [the officer] under the totality of the circumstances."

This case will will have a significant impact because up until now various courts in California have not been in agreement with regard to voluntary encounters with law enforcement, with some lower courts finding 4th Amendment violations, and some finding no violation at all. As a result of the Linn case, the courts can now evaluate said voluntarily encounters in a much more consistent manner, which is better for everyone who has encounters, voluntarily or not, with law enforcement.