A handsome robbery detective at the 12th Precinct who dates Kate Beckett briefly after meeting her at the gym and working cases with her. As their relationship progresses, a rivalry develops between him and Richard Castle for Beckett's attention, with both trying to impress her with their skills at crime-solving. Eventually, Beckett breaks off the relationship when she realizes that she has come to care for Castle.
At one point, he worked with Javier Esposito when both were assigned to the 54th precinct and the two remained on good terms until Demming gets transferred to the 12th.
In his spare time, he coaches in a basketball league for disadvantaged kids.
He once recovered a priceless treasure that was stolen from the owner of a Chinese food carry-out restaurant and dated back to the Ming Dynasty. In gratitude, the owner delivers to him, but no one else.
He is played by actor Michael Trucco.