Sophina Brown has signed up to be the new female lead on CBS crime drama Numb3rs.

The actress, who is best known for her role as Shark's Raina Troy, had previously agreed to star in the first three episodes of the new season. However, producers decided to promote her to a series regular after she impressed them with her performance as agent Nikki Betancourt, a former LAPD officer.

Executive producer Ken Sanzel, himself a former police officer, revealed that he is most pleased with the interactions between Nikki and David Krumholtz's character Charlie Eppes.

"Sophina brings a brand new voice to the show," Sanzel told Entertainment Weekly. "She captures Nikki's grit, humour, and fresh perspective on not only Charlie's role with the FBI, but the FBI itself.

"From the day she came in and auditioned, she owned the character. It's hard for an actor to convince an ex-cop that she's an ex-cop. Sophina convinced me."

Brown is seen as a successor for Diane Farr, who chose to leave her role as lead female character Megan Reeves this year.

Numb3rs returns for its fifth season on October 3 in the US.