A Detective Point is a function in LEGO City Undercover and LEGO City Undercover: The Chase Begins. Using them makes trails of footprints appear, which you can follow to find a hidden object.
LEGO City Undercover[]
In LEGO City Undercover, they allow the player to start using the Detective Scan feature on the Communicator.
LEGO City Undercover: The Chase Begins[]
In The Chase Begins, Detective Points activate Detective Mode, which is the same as the Detective Scan feature in LEGO City Undercover, except you use a magnifying glass to track the footprints instead of the Communicator.