On July 7, 2010, a suspect, Lonnie David Franklin Jr., 57, was arrested. Los Angeles County District Attorney, Steve Cooley, charged him with ten counts of murder, one count of attempted murder, and special circumstance allegations of multiple murders in the case.

Investigation

After police discovered several dead women in alleyways and dumpsters in South Los Angeles, California during the mid-1980s, Los Angeles County Sheriff's Department and police began investigating the murders setting up the "Southside Slayer" task force. At the time, the police thought that the murders were committed by one person labelled the "Southside Slayer".

These crimes were announced to the public on September 23, 1985. Eventually, the LAPD and the Sheriff's detectives realized that several serial killers were murdering women and it was a difficult task for the detectives to decide which murders were linked. Amongst their other murders, Louis Craine and Daniel Lee Siebert committed at least two of the murders each, and Ivan Hill and Michael Hughes at least one each.

A separate series of killings commenced with the murder of Debra Jackson, with a different MO involving a firearm. These became known, misleadingly, as the Strawberry Murders. Two decades later the perpetrator of these crimes was named Grim Sleeper due to a long period of apparent inactivity between crimes.

In May 2007, the murder of Janecia Peters, 25, was linked through DNA analysis to eleven, possibly twelve, unsolved murders in Los Angeles, the first of which occurred in 1985. The "800 Task Force" was then formed, consisting of seven detectives.

After a four-month investigation, the LA Weekly investigative reporter Christine Pelisek broke the news of the secret 800 Task Force, the linking of Peters' killing to a string of murders going back 23 years, and the fact that Mayor Antonio Villaraigosa and Police Chief William Bratton had been silent on the killer's existence. The mayor and chief never issued a press release nor warned the South Los Angeles community of the killer's continuing activities. In some cases, the alternative newspaper was the first to inform the families that their daughters had long been confirmed as victims of a serial killer.

In March 2009, Christine Pelisek of the LA Weekly did an extensive interview with Enietra Washington, the sole survivor of the Grim Sleeper's attacks. She described him as "a black man in his early 30s [...] He looked neat. Tidy. Kind of geeky. He wore a black polo shirt tucked into khaki trousers." She also described him as a "thin, neat, polite and well-groomed African-American guy." He owned "an orange Ford Pinto with a white racing stripe on the hood." "[I]t looked like a Hot Wheels [toy] car," the survivor recalled. He offered her a ride. After she refused, "He told me, ‘That is what is wrong with you black women. You think you are all that.'" He was persistent. After some banter back and forth, she got into his car. She "was impressed by the car’s interior. The gear-shift handle was memorable, pimped out with a ping-pong-sized marble ball. The inside was all-white, with white diamond-patterned upholstery."

When she mentioned a party, he deftly invited himself and she said he was welcome to come. He then said that he needed to stop briefly at his uncle's house: "They wound through residential roads in his sporty car, ending up on a street whose name she did not take note of. The polite stranger parked outside a mustard-colored house partly obscured by hedges, got out, walked up to the house, briefly talked to someone inside, and returned about ten minutes later." They began arguing, when "He suddenly pulled a small handgun out of a pocket on the driver’s side of the Pinto, and shot her in the chest as he drove along the residential streets."

The killer apparently documented his attacks with a Polaroid camera: "She blacked out, but was startled awake by the bright flash of the camera. The man had taken her picture and sexually assaulted her. She remembers grabbing at him, and the two struggled. She pleaded to be taken to a hospital. He refused. Despite her half-conscious condition, she’s almost certain he told her he couldn’t take her to a hospital because he didn’t want to get caught."

In late August 2008, the same week the Weekly broke the sole survivor's story with information on the Grim Sleeper's body count of thirteen victims, an aide to Police Chief William Bratton said he was too busy to comment on the case.

In early September 2008, officials in Los Angeles announced that they were offering a $500,000 reward to help catch the killer, who has murdered at least ten women and a man in two sprees over the past twenty years.

On November 1, 2008, a story about the "Grim Sleeper" appeared on the television program America's Most Wanted. The program stated that the killer was most likely a black male but did not want to rule out anyone.

On February 25, 2009, for the first time, Chief Bratton held a press conference regarding the case at which police formally gave the killer the "Grim Sleeper" nickname chosen by L.A. Weekly. Bratton then released a call from the 1980s made to a 911 operator in which a man reports having seen a body, which later turned out to be a victim of the Grim Sleeper, getting dumped by the killer, with a detailed description and license plate number of a van connected with the now-closed Cosmopolitan Church.

In December, 2009 the LAPD re-released the original police sketch of the Grim Sleeper, based on the description given to them in 1988 by his only known survivor Enietra Washington: the sketch shows a black male with pockmarks across both cheeks.

In December, 2009 the LAPD also released three age-enhanced composite drawings showing the markedly different faces of three middle aged black males.

Arrest

On July 7, 2010, the Los Angeles Times reported that an arrest had been made. District Attorney Steve Cooley identified the suspect as 57-year-old Lonnie David Franklin Jr., a mechanic who worked between 1981 and 1989 for the City of Los Angeles in the sanitation department and briefly for the police department. The arrest of Franklin reportedly was due, at least in part, to the use of familial DNA analysis.

Police had been unable to find an exact match between DNA found at the crime scenes associated with the Grim Sleeper and any of the profiles in California's DNA profile database. Thus, police searched the database to try to find stored profiles that demonstrated sufficient similarity to the profile from the crime-scene evidence to allow police to infer a familial relationship between the person who left the DNA at the crime scenes and the similar profile stored in the database.

Police eventually located similar DNA belonging to Franklin's son, Christopher, who had been convicted of a felony weapons charge. According to Los Angeles District Attorney Steve Cooley, detectives then used a piece of discarded pizza with Franklin's DNA to make the link. One Los Angeles undercover police officer pretended to be a waiter at a restaurant where the suspect ate. He collected dishes, silverware, glasses, and pizza crusts to obtain DNA. The identification was used to arrest Franklin after his DNA was obtained and deemed a match. Saliva found on victims' breasts was used to obtain a DNA match thus linking Franklin to the murders.

Law enforcement missed an opportunity to catch Franklin because his DNA was never collected. In 2003, he was convicted of a felony and was serving three years of supervised probation. When he was on probation, his DNA was supposed to enter the DNA database. In 2004, voters approved of Proposition 69. The law states that DNA must be collected for all people charged with a crime. It also requires the expansion of the DNA database. Authorities collected and sorted through thousands of DNA samples.

On July 2005, Franklin was on unsupervised probation. During that time, Franklin's DNA never entered into the system. Probation officers did not collect DNA samples from people that are on unsupervised probation between the periods of November 2004 and August 2005. During that period, the probation department also did not have the resources to immediately collect samples. Officers did not collect samples until August 2005.

Franklin has a criminal record dating back to 1989. He was convicted of two charges of stolen property, one charge of misdemeanor assault, and one charge of battery. He served time for one of the charges of stolen property. He is charged with 10 homicides and 1 attempted murder. He is held without bail and could face the death penalty if convicted. He is not charged in the death of an 11th suspected victim, an African American man. There is no DNA evidence in that case.

On December 16, 2010, the Los Angeles Police Department released 180 photos of women found in Franklin's home. Police officials released the images after unsuccessful attempts to identify the individuals, possibly additional victims. "These people are not suspects, we don't even know if they are victims, but we do know this: Lonnie Franklin's reign of terror in the city of Los Angeles, which spanned well over two decades, culminating with almost a dozen murder victims, certainly needs to be investigated further," said Chief Charlie Beck of the LAPD. In all, investigators found over 1,000 photos and several hundred hours of video in the home.

The images show mainly African American women of a wide age range, from teenagers to middle-aged and older, often nude. Police believe Franklin took many of the pictures, which show both conscious and unconscious individuals, and date back up to 30 years. The photos were released in an effort to identify the women with the help of citizens.

Victims

The known killings began in 1985 in South Los Angeles, California. The Grim Sleeper took a 14 year hiatus after his last murder in 1988 but began murdering again in 2002. His last confirmed murder was in January 2007. All of his victims were found outdoors, a few miles from downtown Los Angeles.

All but one of his victims were black females. One of his suspected victims was a black man. Many of his victims were prostitutes. One witness recalls that Franklin would frequently bring prostitutes into his home. The Grim Sleeper would have sexual contact with victims before strangling or shooting them. He would shoot all of his victims with a .25 caliber gun. Franklin took several photographs of nude prostitutes and kept them in his garage.

These are the Grim Sleeper's known victims in chronological order of attack:
 

^‡ One of the Grim Sleeper's suspected victims, though there is no DNA evidence to support this claim. Being the only suspected male victim, it is believed that Steele either knew about Grim Sleeper's history of murders, or that he was friends with one of the victims.
^‡‡ Enietra "Margette" was told to use her middle name as her last name for her protection, but has since come forward as Enietra Margette Washington. Attacked on November 20, 1988, she is the only known survivor. After her escape, there were no other known attacks for almost a decade and a half