Thanks to one of Sienna’s biggest fans, Galijabre, I learned that Sienna will appear in the famous American TV series, CSI, in the 11×01 episode “Blow”, where she will play a lab tech named Kacey Monohan.
Sienna said: “We have just started shooting and the atmosphere is electric,” the actress confirmed. “I suggest everyone holds on to their haircuts because my character is going to blow fans away, literally. She’s the team’s first full-time bomb tech and the action scenes will be explosive in every sense.”
She confirmed it also in her twitter account! 
It seems that Sienna will also star as guest star in the TV show Covert Affairs for one episode! It has not been confirmed, yet!
SOURCE
Auteur : Ricky 06.08.2010 (14) Commentaires
Aug 7, 2010
U said it all right Ricky ! I think that Sienna is in Covert Affairs but no one knows what kinda character she plays. It is soo cool that Sienna joined CSI and that she is acting with Justin Bieber.Sienna said that her character is gonna BLOW HER FANS AWAY !