A Los Angeles County jury on Monday pronounced a death sentence for the serial killer known as the "Grim Sleeper".  Jurors rejected defence arguments that Lonnie David Franklin Jr., who was convicted last month of 10 murders committed between 1985 and 2007, should spend the rest of his life in prison rather than face execution.

He will be formally sentenced at a later hearing.

According to the Los Angeles Times, the deaths that occurred in the mid-to-late-'80s coincided with a surge in slayings linked to the crack cocaine epidemic. Grim Sleeper preyed on some of the city's most vulnerable .

The Grim Sleeper targeted women who were drug addicts or prostitutes, and often dumped their naked bodies on the side of roads or in trash. Many of the women were initially listed as Jane Does, a place holder name used to refer to a corpse or hospital patient whose identity is unknown.

Police kept the killings quiet despite suspicions that a serial killer targeting black women was out on the prowl – a decision that led to outrage. Many believe Franklin's longevity as a killer was due to police negligence.

When police raided his home in 2010, they found hundreds of pictures of women – many of them naked and with their eyes closed.

Investigators think Franklin may have killed at least 25 women, some even speculate the number can be significantly higher.

LAPD Det. Daryn Dupree, the last remaining detective on the task force that arrested Franklin, said that police are yet to identify 34 of the women. "We don't know if they're dead or alive," Dupree said.

The victims listed in the charges against Franklin, in the order in which they died, were: Debra Jackson, 29; Henrietta Wright, 35; Barbara Ware, 23; Bernita Sparks, 25; Mary Lowe, 26; Lachrica Jefferson, 22; Alicia Alexander, 18; Princess Berthomieux,15; Valerie McCorvey, 35; and Janecia Peters, 25.

Most of the women were shot to death, and Berthomieux was strangled.

Franklin initially earned the "Grim Sleeper" nickname because a gap in the killings between 1988 and 2002 suggested he had gone dormant. But detectives believe Franklin never really slept.

During the penalty phase of the trial, prosecutors connected Franklin to an additional five killings but the district attorney's office decided not to charge him because he was already facing death penalty and prosecutors did not want to further stall the trial.

Georgia Mae Thomas, 43, one of the five, was killed in 2000. Prosecutors said the other additional victims were Inez Warren, 28; Rolena Morris, 31; Sharon Dismuke, 21; and Ayellah Marshall, 18.

Morris vanished in 2005 and Marshall disappeared in 2006. Their bodies were never found.

Marshall's Hawthorne High School ID card and a photograph of Morris, along with her driver's licence, were found inside a garage refrigerator in Franklin's house stuffed with a morbid cache of items, including women's underwear and other photographs. Prosecutors called it Franklin's "trophy case."

According to the BBC, Franklin was eventually caught after detectives began working on the final killing in 2007 when DNA from his son, who was in prison, showed similarities to genetic evidence found on some of the victims.

A detective posing as a worker in a pizza parlour later collected utensils and crusts from Franklin while he was attending a birthday party. DNA tests connected him to evidence found on several of the bodies.