The trial for Catherine Kieu, 50, began Wednesday in Orange County, the Los Angeles Times reported.
She faces felony charges of torture and aggravated mayhem, with a sentencing enhancement for the personal use of a knife, the Orange County district attorney's office said.
Prosecutors say Kieu drugged her 60-year-old husband's dinner July 11, 2011, then tied him to the bed, and cut off his penis and threw it in the garbage disposal.
Kieu's husband, whose name was not reported, was treated and released from the University of California Irvine Medical Center. Doctors were unable to reattach his penis.
A voice-activated audio recorder Kieu had placed in the bedroom appeared to catch her repeatedly yelling, "You deserve it," at her husband during the incident, The Orange County Register reported Wednesday.
Deputy Public Defender Frank Bittar said Kieu should not be convicted because she suffered from post-traumatic stress disorder from her childhood in war-torn Vietnam in the 1960s. He said she was raped repeatedly by her brother after their mother died.
Deputy District Attorney John Christl argued the attack was premeditated and committed out of "vengeance, vanity and jealousy."
If convicted, Kieu could face life in prison with the possibility of parole, the Times reported.