McNamara grew up in Oak Park, Illinois, the daughter of Thomas W. McNamara, a trial lawyer, and Rita McNamara, a stay-at-home mother. Her parents were Irish American. McNamara was the youngest of the couple's five daughters and one son. They grew up Irish Catholic. In 1988, she graduated from Oak Park and River Forest High School in Oak Park, Illinois, where her senior year she was editor-in-chief of the student newspaper, the Trapeze. In 1992, McNamara graduated from the University of Notre Dame with a bachelor's degree in English. She earned an MFA in creative writing from the University of Minnesota.
Career
After graduate school, in 1997 McNamara moved to Los Angeles to write in the film and TV industry. In 2006, McNamara launched her website TrueCrimeDiary. McNamara had a long-standing fascination with true crime originating from the unsolved murder of Kathleen Lombardo that happened two blocks from where she lived when she was young. In 2014, McNamara and true crime investigative journalist Billy Jensen were on a SXSW Interactive panel called "Citizen Dicks: Solving Murders With Social Media." McNamara and Jensen had a long-term friendship based on their shared passion for researching and writing about true crime. McNamara became interested in the crimes of the unidentified rapist and murderer known as the "East Area Rapist", "Original Night Stalker" and the "Visalia Ransacker", among other epithets. Due in large part to McNamara's efforts in tying these crime clusters together in public consciousness after the EAR and ONS crimes were linked by DNA, the murderer was later to be known exclusively as the Golden State Killer. She penned articles for Los Angeles magazine about the serial killer in 2013 and 2014. Paul Holes, an investigator for the Contra Costa County district attorney's office, stated that McNamara's dogged persistence and trustworthiness with sensitive information about GSK cases earned her an unusual level of cooperation from law enforcement officials. She then signed a book deal with HarperCollins and began to work on a book about the case. Her book, titled I'll Be Gone in the Dark: One Woman's Obsessive Search for the Golden State Killer, was posthumously updated and finalized by true crime writers Paul Haynes, Billy Jensen and her widower Patton Oswalt following her death. The book, released posthumously on February 27, 2018, reached number 2 of The New York TimesBest Seller list for non-fiction and number 1 of combined print and e-book, nonfiction. The book remained on the list for 15 weeks. On April 9, 2018, HBO announced that they had purchased the rights for I'll Be Gone in the Dark and were developing it into a documentary series. Filming for the series began on April 24, 2018. The documentary series, also entitled I'll Be Gone in the Dark, is directed by Liz Garbus and premiered on June 28, 2020. On the evening of April 24, 2018, Californian authorities arrested Joseph James DeAngelo as the alleged Golden State Killer at his home. Oswalt claimed that authorities' use of the killer's name that McNamara coined was "proof of the impact of her work."
Personal life
McNamara married comedian Patton Oswalt on September 24, 2005. The couple's daughter Alice was born on April 15, 2009.
