We conclude that Officer Brown's call for back-up, when combined with his other conduct, would convey to a reasonable person that he or she was not free to refuse to answer Brown's questions or otherwise terminate the second stage of the encounter. More specifically, both before and after making the call, Brown repeatedly asked Thomas questions about her drug use and possession. After the call, Thomas emptied her pockets for him, apparently in an attempt to prove her denials. He then asked to feel inside her pockets, and she threw her hands in the air. After Brown again told Thomas to "be honest with me," she confessed to possessing two crack pipes. In contrast to the first stage, at no time during the second stage did Brown tell Thomas she was free to leave.The KSC went on to hold that the officer did not have reasonable suspicion to detain Ms. Thomas and, therefore concluded that the motion to suppress should have been granted.
This a nice example of how, even when an officer asks "Can I ask you just a couple more questions?" (i.e. the Lt. Columbo gambit), it does not necessarily make the resulting encounter voluntary. The circumstances of the resulting encounter still determine that question.
Here is coverage on FourthAmendment.com.