In a recent criminal defense case the interaction between an officer and the Defendant was a mere "encounter" rather than an investigative detention in Hughes v. State because the officer activated the squad car's white overhead lights rather than the red and blue lights. Also, the position of the car relative to the defendant's vehicle did not entirely prevent the defendant from leaving.
The officer observed the suspect's car in a parking lot of a park that was legally parked with the headlights on. As the officer approached, the headlights of the criminal defendant's vehicle turned off. The officer parked his marked police jeep at an angle to the defendant's car and turned on the bright overhead white lights. The officer then illuminated the front of the defendant's vehicle with his spotlight. He testified that he did no observe any illegal activity, but that the park area has a high incidence of drug and prostitution activity. The lights activated by the police officer in this case were not his overhead emergency lights which flash red and blue, but rather the overhead white safety or "take-down" lights.
The court believed that distinction to be extremely important. Under some circumstances, overhead lights that are "take-down" lights could be sufficient along with other circumstances to indicate a sufficient demonstration of authority.
If an investigative detention occurs, then the fourth amendment protection against warrantless searches and seizures is implicated. However, where there is merely a police encounter, there is no protection for a citizen who is ultimately accused of committing a crime. There are many different levels of police encounters, from just a casual crossing of the paths with a citizen to restricting their ability to leave freely by making an arrest.