Los Angeles (CNN) Lonnie David Franklin, Jr., a one-time garbage truck driver and LAPD garage attendant, was found guilty Thursday of murdering nine women and one girl over a span of three decades, making him one of the most prolific serial killers in California history.

Jurors took less than two days to convict Franklin of all charges against him, including the attempted murder of a woman who survived a 1988 attack. He was dubbed "The Grim Sleeper" because of a 13-year gap between slayings attributed to him.

Franklin, who has close-cropped hair and wears glasses, stared straight ahead and remained silent during the several minutes it took the court clerk to read the verdicts.

Family members of the victims, who had been cautioned by the judge to refrain from displays of emotion, quietly comforted and congratulated one another with each passing "guilty." Some nodded their heads in approval.

The trial in Los Angeles County Superior Court will now go to the penalty phase, beginning May 11, in which jurors will be asked to decide whether Franklin, 63, should be put to death for his crimes. Prosecutors disclosed Wednesday that two more women — one he was convicted of raping and another he attempted to kidnap and rape in Germany while in the U.S. Army in the 1970s -- may testify during the penalty phase of his trial.

Outside the courtroom after the verdicts were read, Samara Herard, sister to Franklin's youngest victim, 15-year-old Princess Berthomieux, said she was not surprised at the killer's lack of reaction.

"He doesn't value life," Herard said. "He doesn't care."

Herard said she was grateful for the jury's decision. But she prefers to think of her sister not as a victim, but as the person she was before she encountered Franklin.

"I want to remember the sweet little girl who had her whole life in front of her," she said.

'They are all premeditated'

The verdict follows a three-month trial featuring the testimony of 61 witnesses. Prosecutors portrayed Franklin as a sexual predator who killed his victims, then dumped their bodies like the trash he was paid to collect.

"He did it over, and over, and over, and over and over, and over," Deputy District Attorney Beth Silverman told jurors during closing arguments. "All of the murders in this case are first degree. They are all willful. They are all deliberate. They are all premeditated."

Lonnie David Franklin Jr., the accused "Grim Sleeper."

Franklin's defense attorney, Seymour Amster, told jurors during his closing that the government's case was "circumstantial" and lacked the evidence required for a conviction. He suggested that an unnamed relative of Franklin's committed the killings, but offered no proof.

"The lack of evidence in this case compels you to find Mr. Franklin not guilty," he told jurors.

The lawyer also issued an apology for his own behavior during the trial, which was marked by moments of visible frustration and terse exchanges with the judge and prosecutor. He at one point said, "We now have no defense," following an unfavorable ruling by Judge Kathleen Kennedy.

"Just do your job," Kennedy told him.

'Body dumps'

Jurors clearly were not swayed by the defense Amster ultimately put on.

Police linked Franklin to the crimes in 2010 using DNA technology that did not exist when the initial killing spree occurred in the 1980s, according to prosecutors. Their case was built on that DNA evidence, including Franklin's saliva on many of his victims' breasts, along with ballistic evidence and the testimony of a surviving victim.

Silverman spent much of her closing arguments walking jurors through evidence in the case, including DNA, which she acknowledged can be "very tedious."

She spoke of astronomical odds — in the quadrillions and quintillions — that DNA collected from victims and crime scenes belonged to someone other than Franklin.

She noted the common characteristics between many of the crime scenes in which victims were found in alleys and dumpsters in South Los Angeles, all of them within a few miles of Franklin's home. Most wore disheveled clothing suggesting they'd been re-dressed and moved. They carried no identification.

Each of the crime scenes bore one or more characteristics of a "body dump," in which a victim is killed in one location and discarded in another, Silverman told jurors.

A surviving victim

The prosecutor also cited the testimony of a surviving victim who she said "provides a blueprint for the murdered women who cannot speak and can't tell you what happened."

That victim, Enietra Washington, testified that Franklin coaxed her into his orange Pinto in 1988 and, without warning, pulled out a handgun and shot her in the chest. She remembered Franklin climbing on top of her and a camera flashing as she lost consciousness.

He pushed her out of the moving car, assuming she was dead, Silverman said.

When detectives searched Franklin's house two decades later they found pictures of Washington hidden behind a wall, Silverman told the jury.

The prosecutor also reminded jurors of a videotaped police interrogation of Franklin, played during the trial, in which she said the accused killer did not appear surprised about the allegations against him. He laughed at times and called one victim "fat" and another "butt ugly" as detectives showed him photos.

"They're staring up at him — and he's laughing in their faces," Silverman said of the defendant.

DNA evidence to the rescue

Franklin had been charged with killing 10 victims, ranging in age from 15 to 35, from 1988 to 2007. He was also charged with the attempted murder of Washington.

The first spree began in the summer of 1985 and seemingly ended three years later. Police did not know his identity at the time but had linked seven slayings to the same .25-caliber handgun.

The then-unknown killer apparently fell dormant for years. Decades later, in 2007, LAPD homicide detectives got word from the department's forensic lab of "case to case hits" linking one person's DNA to unsolved slayings in 2002, 2003 and 2007, according to Detective Dennis Kilcoyne.

Detectives were unable to match the killer's DNA to any known samples contained in databanks. The department formed a task force that soon discovered the killings in the 2000s were connected to the unsolved spree in the 1980s, Kilcoyne wrote in a statement submitted to a congressional subcommittee investigating the use of DNA in so-called cold cases.

In 2008, detectives submitted crime scene DNA from both sprees to the California Department of Justice, asking them to conduct a "familia search" to determine if a close relative of the unknown killer was in a state databank of convicted felons' DNA.

The search came back negative.

But a second attempt, conducted two years later, yielded a hit, Kilcoyne wrote. It matched the DNA to a recently convicted felon.

The criminal's father turned out to be Franklin, according to authorities.

The pizza plan

Detectives placed Franklin under 24-hour surveillance and came up with a plan to obtain a sample of his DNA.

An undercover officer posed as a waiter at a local restaurant and collected a pizza crust left behind by the suspect. DNA taken from the crust matched DNA left by the suspect in multiple murders, Kilcoyne wrote.

Franklin was arrested in July 2010.

When police raided his South Los Angeles home, they discovered photos and videos of dozens of unidentified women. Police have since accounted for the identities and whereabouts of some of the women, but others remain unknown.

Silverman called Franklin a "serial killer who was hiding in plain sight."

"Science in 2010 finally caught up with the defendant for the crimes he committed since the 1980s," she said shortly before the case went to the jury. "All of the evidence in this case proves the defendant is guilty beyond any reasonable doubt. There is no other plausible explanation."

Police Chief Charlie Beck, in a statement, said he hoped the verdict would bring "some closure for these families."

After Thursday's verdict, reporters crowded around relatives of the victims. Herard, Berthomieux's sister, kept her composure as she spoke about Princess in front of a throng of TV cameras.

Moments later she embraced Kilcoyne, the LAPD detective who played a pivotal role in the investigation.

"Thank you so much," she whispered again and again to him, tears welling in her eyes.