The significance of this case is that it helps to define when a person has been seized/arrested. In this case, the Supreme Court ruled that an arrest only happens when the person has been physically seized or when they have submitted voluntarily to the authority of the police.
In this case, a youth ran from the police when told to stop and be searched. As he ran, he threw away some crack cocaine. His lawyers later argued that, at the time when he threw the crack away, he was under arrest. They further argued that the arrest was illegal.
The Court ruled that he was not under arrest because the police had not physically touched him and he had not submitted to their orders. Therefore, there was no arrest, illegal or otherwise, and the crack could be used as evidence.
The significance of this case is that it helps to clarify when an arrest has occurred.