Born in Baltimore, Maryland, and raised in Clarendon Hills, Illinois, Harris was the daughter of Frederick Schwartz, an engineer, and had a middle-class upbringing. She graduated from Indiana University with a bachelor's degree in language arts, having earned straight A's.
Emily and Bill Harris arrived in Berkeley, California in 1973 from Bloomington, Indiana. They came with their friends Gary Atwood and Angela Atwood. They soon joined a left-wing group that, among other things, visited prisoners in northern California. The Harrises met an escaped prisoner, Donald DeFreeze. They joined the SLA, created by Mizmoon Soltysik, Nancy Ling Perry, Joe Remiro, Russ Little, Willie Wolfe, Angela Atwood, Thero Wheeler, and Camilla Hall. Emily Harris's nom de guerre was Yolanda. On November 6, the SLA committed its first public act, the assassination of popular Oakland, California school superintendent Marcus Foster. The SLA mistakenly thought that Foster was behind a plan to create student identification cards for Oakland high schools. Subsequently, they kidnapped Patricia Hearst, the college student heir to the Hearst newspaper chain.
Emily and Bill Harris took over the leadership of the SLA after six other SLA members died in a Los Angeles shootout with police and the house fire it triggered. After the fire, the Harrises spent over a year eluding the authorities with their victim, Patty Hearst, and new members Kathleen Soliah, Josephine Soliah, Steven Soliah, Mike Bortin, Jim Kilgore, and Wendy Yoshimura. Hearst herself had since become a participant in SLA crimes. Yoshimura, Patty's closest friend while underground, was a fugitive for her involvement with explosives that were stored in a garage she rented. During that year the SLA committed a string of crimes, including an April 21, 1975 robbery of Crocker National Bank in Carmichael, California. During the robbery, 42-year-old Myrna Opsahl was shotgunned to death. Opsahl was depositing a church collection at the time. Patty Hearst stated in her 1982 autobiography Every Secret Thing that Emily was the shooter. Hearst also stated that Harris said, "Oh, she's dead, but it doesn't really matter. She was a bourgeois pig anyway. Her husband is a doctor." Other SLA members had urged Harris not to bring the shotgun to the robbery, as it had accidentally discharged twice during preparations.
The Harrises were eventually arrested and served eight years in prison for the Hearst kidnapping. Imprisoned at the California Institution for Women at Frontera, California, Emily Harris spent the first half of her term in solitary confinement. Emily learned computer programming in prison.
After her release from prison in 1983, Harris became a computer programmer and began a successful computer consulting company. She worked at MGM Studios until her second conviction. She divorced her husband.
For over 25 years no one was charged in the Opsahl murder. The SLA wore wigs and masks during the Crocker Bank robbery, and left little evidence behind. However, with new forensics techniques, the FBI was eventually able to link shotgun pellets removed from Opsahl's body to shotgun shells found in an SLA hideout. Additional evidence mounted, and in 2002 Harris and three other SLA members were charged with the Opsahl murder. Harris's bail was set at one million US dollars, which her supporters quickly gathered.
Three former SLA members who had been granted immunity - Hearst, Steven Soliah, and Wendy Yoshimura - were set to testify for the prosecution in the Opsahl case.
Facing a possible conviction, Harris and the others pleaded guilty to second-degree murder. Harris was sentenced to eight additional years in prison; Bill Harris was sentenced to seven years and Kathleen Soliah and Michael Bortin were each sentenced to six years for their roles.