Serena Benson (February 3, 1944-December 10, 2000) was an English professor at Columbia University, and the mother of Sergeant Olivia Benson from the Manhattan Special Victims Unit. She was one of the major inspirations for her daughter's joining that particular unit.
Serena was an alcoholic who emotionally abused Olivia.
The only time audiences ever saw Serena was in "Payback". Olivia and Serena were having dinner. When Olivia started talking about the case she was working on, Serena expressed her concern about Olivia working in the Special Victims Unit. Serena also seemed to have accepted the fact that she was raped and that the rape produced a child.
In the episode "Haystack", Olivia runs her DNA through a kinship analysis and discovers she has a half brother. From Simon Marsden, she learns about the man who fathered her (SVU: "Philadelphia"). Simon's description of his father leads Olivia to doubt Serena's rape allegation but another one of his victims, Jane Willet-Marcus, confirmed that Joseph Hollister was a rapist. From Simon's mother Sharon Marsden, Olivia learned that Hollister knew about her and at least once called her house but Serena answered the phone. (SVU: "Florida")
When her daughter was 16, the two got into a fight after Olivia announced that she had accepted a proposal of marriage from one of Serena's students. An intoxicated Serena went after Olivia and Olivia kicked her into a wall, knocking her unconscious. Olivia retained the services of then-law student Simone Bryce to avoid jail. (SVU: "Intoxicated")
On December 10 2000, Ms. Benson came out of a bar called the Velvet Room and took a fatal tumble down the stairs. (SVU: "Taken" [Continunity error: whilst the episode originally AIRED in December 15, 2000, the actual episode had titlecards with dates between September 6-15th], "Hammered" [When Olivia visits Serena's grave, the date on the headstone is December 10, 2000]) This was the first time Olivia stated her mother was an alcoholic.