Marg Helgenberger turns in her badge on Wednesday night, stepping away from the Catherine Willows character she has played on the CSI crime drama for 12 seasons.

It's kind of hard to comprehend, Helgenberger said, as reported by E! Online. It's just been a fifth of my life. It's something that was extraordinarily rare -- television and a once in a lifetime thing most people don't even have. From the pilot on it's been touched with magic dust, so I've been very aware of how special it's been.

Helgenberger began collecting fingerprints and analyzing blood spatter since 2000 when the show began. Helgenberger's Catherine Willows character began making her exit in a two-part episode. The first episode aired Jan. 18 and the other Wednesday. Willows is leaving the Las Vegas crime lab for a federal post in Washington.

I felt the need to kind of step back, because I had been playing this character for 11 and a half years, to reassess and regroup and I'm -- as scary as that is -- I'm also very excited about the great wide open, the future and all the possibilities, Helgenberger has said about her leaving.

Helgenberger has also said she is open to a return to the show.

Watch a sneak peek of Catherine Willows' last episode below: