|Minor Character: Las Vegas|
|Family|| Unnamed ex-wife|
|Portrayed By||Alex Carter|
Detective Louis "Lou" Vartann is a homicide detective at the Las Vegas Police Department.
Vartann has a 21 year old son. (The Panty Sniffer) His ex-wife got custody of his son during the divorce, but his son was a handful and so Vartann got custody when his son was in high school. His son no longer lives at home, and Vartann misses having someone to come home to.
During Season 10, it is shown that Lou is having a relationship with Catherine Willows.
In Blood Moon, Catherine and Lou are having sex with each other and then even discuss moving in with each other but Catherine says that that the relationship is moving to quick and that she would just like then to take things slower, so that they can carry on their purely sexual relationship.
Vartann believes Las Vegas has no history, that history in Vegas gets imploded. (Bang-Bang)
- Season 4: Grissom Versus the Volcano, Eleven Angry Jurors, XX, Dead Ringer, Bloodlines
- Season 5: Viva Las Vegas, Crow's Feet, Mea Culpa, No Humans Involved, Big Middle, Spark of Life, 4x4, Weeping Willows, Iced
- Season 6: Bodies in Motion, A Bullet Runs Through It, Part 1, A Bullet Runs Through It, Part 2, Bang-Bang
- Season 9: Art Imitates Life, Let It Bleed, 19 Down, Deep Fried and Minty Fresh, Kill Me if You Can, Turn, Turn, Turn, The Gone Dead Train
- Season 10: Death and the Maiden, Better Off Dead, The Panty Sniffer
- Season 11: Blood Moon
- Season 12: Ms. Willows Regrets, Seeing Red
- Season 13: Dead Air
- Although his full name is Louis, everyone refers to him as Lou.
- He is an alcoholic, but has been sober for over 15 years. (The List)