Los Angeles Jury Finds 'Grim Sleeper' Serial Killer Guilty of Murdering 10 Women in 23-Year Killing Spree

After a day and a half of deliberations, a Los Angeles jury has found Lonnie Franklin, the so-called Grim Sleeper serial killer, guilty of the murder of 10 women and the attempted murder of another in South Los Angeles during a 23-year killing spree.

The verdict brings to an end a nearly three-month trial featuring the testimony of more than 50 witnesses, including Grim Sleeper survivor Enietra Washington, who testified that Franklin shot her, sexually assaulted her, and took a Polaroid picture of her before pushing her out of his car 27 years ago.

"God is good," Mary Alexander, whose daughter Monique was killed in September of 1988, tells PEOPLE in the wake of the verdict.

The penalty phase of the trial will begin May 12.

Franklin, a married father of two and former LAPD mechanic and sanitation worker for the city of Los Angeles, was charged with the murders in July of 2010.

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Most of Franklin's victims were shot with a .25-caliber pistol while others were strangled. Their bodies were discovered in dumpsters and alleyways along Western Avenue in South Los Angeles, an area known for its cheap motels, liquor stores, gambling parlors, auto salvage yards and storefront churches.

His murder spree began on Jan. 15, 1984, when Sharon Dismuke was discovered fatally shot in the chest in the restroom of an abandoned gas station.

The last known murder occurred on January 1, 2007, when 25-year-old Janecia Peters's lifeless body was discovered in a dumpster. Peters had been shot in the lower back, paralyzing her from the waist down.

"She couldn't run away," said prosecutor Beth Silverman during closing arguments Monday. "She couldn't escape. This particular victim spent several minutes gasping for breath. It was an agonizing way to die."

Prosecutors portrayed Franklin as a opportunistic killer who hunted for his victims in the same area in which he lived and worked. The majority of his victims were found within a few miles of where Franklin lived.

"He is a serial killer who was basically hiding in plain sight," Silverman said. "He blended in. All evidence points to one person as the killer."

Silverman said Franklin was a "sexual predator," who killed women who "weren't submissive enough."

"These crimes were about power and control," she told the jury. "It is clear the defendant got pleasure from killing these young women because that's how they all ended up. He definitely wanted to degrade these women by dumping their bodies like trash. He got off on that too and that is why he did it over and over. It gave him gratification."

During closing arguments, Franklin's defense attorney Seymour Amster suggested that a "mystery man," possibly a "nephew" or someone who referred to Franklin as his "uncle," was the real culprit.

"Each and every murder in this case could have been done by a mystery man with a mystery gun with mystery DNA," he told jurors.