|Main Character: Las Vegas|
|Birth Date||March 26,1963|
|Family|| Lily Flynn (mother)|
Sam Braun (father)
Eddie Willows (ex-husband)
Lindsey Willows (daughter)
Tony Braun (half-brother)
Walt Braun (half-brother)
|Job|| CSI, Assistant Night Shift Supervisor
|Rank||CSI Level 3|
|Portrayed By||Marg Helgenberger|
Catherine Willows is a former assistant night shift supervisor for the Las Vegas Crime Lab. Before her promotion, she worked as the assistant supervisor under Gil Grissom. After her demotion, she now works under D.B. Russell.  In Willows In The Wind Catherine has resigned from C.S.I and took a job in the F.B.I and then moved to Quantico and Catherine was replaced by Julie Finlay.
She is a Level 3 CSI.
Catherine was willing to do whatever it took to break a case. She even once promised a prisoner that for every question he answered, she would unbutton one button on her blouse. (Leaving Las Vegas)
Catherine has a wide knowledge of odd facts that help in her investigations of crime scenes.  Catherine was a blood-splatter expert and her knowledge on the subject would prove valuable on every case.
On The Job
Catherine had occasional contact with her mother's friend, casino owner Sam Braun, who later turned out to be Catherine's biological father. 
Due to the nature of her mother's jobs, Catherine was constantly moved around the west coast of America as a child and because of this, she found it difficult to settle in school. Consequently, she failed to excel to her full potential in school, despite her high intelligence and razor-sharp mind. 
Catherine herself worked for a time as a dancer/stripper. One of her regular customers was a cop, Jimmy Tadero. (Felonious Monk). She would ask Jimmy what his case of the week was, and he would fill her in on the particulars of the cases he was working on. That triggered an interest in police work which changed the course of her life.
In the episode The Lost Girls, Catherine tells some things about her dancing life to Jim Brass at a night club.
Catherine briefly had a cocaine habit, dropping it before pursuing a Bachelor of Science in Medical Technology from West Las Vegas University. 
Catherine joined the CSI team at LVPD as a lab technician, after which she worked her way up to the role of supervisor under the watchful eye of Gil Grissom. 
In Willows in the Wind, Catherine had decided to leave CSI, due to being targeted by assassins, and take a job in the F.B.I in Quantico. Before she left she bidded farewell to the rest of the team by calling a "Family meeting" at the end of the episode she gave a word of wisdom to Morgan Brody but Morgan had leave for a crime scene.
Catherine was mentioned and contacted by a couple of the CSI team members such as D.B. Russell,Greg Sanders and Nick Stokes in later episodes. And Nick mentions she sounds happy.Catherine was replaced by Julie Finlay.
Catherine has one daughter, Lindsey Willows, and had a stormy relationship with ex-husband Eddie (Timothy Carhart) until his murder (Lady Heather's Box). Prosecution of Eddie's killer proved impossible due to ambiguous evidence, something she took rather hard. Catherine's relationship with Lindsey soured somewhat after Eddie's murder, and the girl's behavior took a turn for the worse; she would get in fights at school and was once picked up for hitchhiking. Catherine took Lindsey to the morgue and showed her the body of a murder victim to impress upon Lindsey the danger of her behavior. Catherine later enrolled Lindsey in Butterfield (4x4), a private school that would keep a tighter rein on her.
Catherine's relationship with Sam Braun occasionally created conflicts in cases where he was involved in some way with an ongoing investigation (i.e., Inside the Box). However, Catherine and Lindsey are now financially stable thanks to a rather large monetary gift from Sam Braun. At the time, Catherine thought the payment was intended to buy her off, but she deposited the check in the end, a matter that caused tension between Catherine and Grissom in an ethics debate. In episode 702 (Built to Kill, Part 2) Braun is shot and dies moments later in Catherine's arms. Catherine, in the episode (Double Cross), lights a candle in a Roman Catholic church in Sam's memory, crosses herself, and whispers, "This one is for you, Sam." It remains to be seen what Catherine will inherit from Braun (Catherine was asked about it by fellow investigator Nick Stokes in Leaving Las Vegas, but beyond describing Braun's large estate as being tied up in land development, she seemed indifferent and not anticipating a large legacy) as he cared very deeply for her, even when she was his legal opponent. But as of the episode "Wild Life", Catherine tells Detective Louis Vartann that Sam left her part of The Eclipse. It is unknown exactly how much she owns.
Catherine dates in several episodes. One brief flirtation, in the episode Weeping Willows, ended when the man (Adam Novak) became overly aggressive. No long-term romantic relationships have otherwise been established, though there was a brief flirtation with fellow CSI Warrick Brown, ending with his marriage, which seemed to upset her. (Bodies in Motion)
Catherine maintains a close friendship with the other investigators on the night shift, especially supervisor Gil Grissom, though she has occasionally criticized him for his lax attitude toward paperwork and office politics. When newcomer Sara Sidle arrived they briefly butted heads, but have become friends since then.
After Greg Sanders is injured in an explosion in the lab (Playing With Fire), Catherine visits him in the hospital so that she can tell him personally that she was partially responsible for the accident. Several years later, she also expresses a deal of concern for Greg when he returns to work not too long after being the victim of a brutal beating (Double Cross).
After Grissom goes on sabbatical, Catherine welcomes his temporary replacement Michael Keppler, accepting Keppler quite quickly into his new role on the team (Sweet Jane). Despite some misgivings on her part, she follows his suggestions in performing an unorthodox investigative style known as "reverse forensics," which, although successful in luring out the suspect, fails to produce charges because a lack of communication between the undersheriff and the district attorney. It also serves to create a great deal of hard feelings when the other members of her team discover that she and Keppler deceived them and created a false crime scene (Redrum). After Keppler goes rogue during an investigation, she is the first to express concern to and about him. Unfortunately, she locates him just moments too late, after he takes a fatal bullet meant for a murder witness. When the paramedics declare Keppler to be dead, Catherine collapses in tears into the arms of the recently returned Grissom (Law of Gravity). Catherine Williows is devastated in the season 9 premiere when longtime co-worker Warrick Brown dies.
- Grissom and Catherine
- Catherine and Warrick
- Catherine and Sara
- Catherine and Sofia
- Catherine and Ecklie
Hatred towards Child Abusers
Catherine has several times had a very strong reaction to cases where a little girl is the victim of their case, to the point where she will allow her own emotions to cloud hers judgement. It is hinted this is because she is the mother of a young girl. Her emotions have caused her to severely jump the gun when it comes to a suspect and showing no hesitation to add her own verbal disgust and disbelief towards a suspect when they tells her their side of the story. Sarah even once sarcastically commented it was fun to hear Catherine's theories rather than "process the actual evidence".  Ironically, every time she has let her emotions take control of a case like this, who her hatred is focused towards has always turned out to be a mere victim of "being at the wrong place at wrong time", shown by the evidence they were in no way involved with the case, but by the time that is revealed she often has completely ruined said guy's life.
Her bias against sex offenders once destroyed a man's life; she believed he was a child molester because of his name on the Sexual Predator Watch List though he was only there because of an incident where got high on hallucinogenics and walked out naked in front of a bus full of children. After the man's fiance found out about his past and that he was using an assumed name, he was kicked out of her house and fired. The man walked up to Catherine in the parking lot after this, threatening to shoot himself in the head on her front lawn one day. 
|CSI:Crime Scene Investigation|
- Catherine's biological father, Sam Braun, called her "Mugs".
- Unknowingly helped to process her half-brother, Tony Braun's, murder scene, which was partially commited by her other half-brother, Walt Braun, ending in his arrest.
- Catherine was born in Bozeman, Montana, the same town from which CSI: NY Detective Lindsay Monroe hails from. Catherine, however, is not typically regarded as a "country girl" as Lindsay Monroe is, possibly because of her tough demeanor, strong personality, and her experiences in Las Vegas prior to her becoming a CSI.
- Catherine identifies Las Vegas as her hometown to the newcomer CSI Mike Keppler, and she has lived in that city most, if not all, her life.
- Though Catherine's birthday is often given as 1963, the episode Living Legend established that she was sixteen years old in 1975, the year that the film Jaws was released. This corresponds more accurately with Marg Helgenberger's real life, as she was born in November, 1958 and Jaws was released in June, 1975, when Helgenberger herself was 16.
- In the video game CSI:Deadly Intent, she states that she was a little girl in 1975.
- Catherine is played by Marg Helgenberger, who has received two Emmy nominations and two Golden Globe nominations for the role.
- Catherine has never had an abortion. (Secrets and Flies)