LOS ANGELES — The death sentence of the “Grim Sleeper” serial killer last week put to rest a case that spanned more than three decades, but it left another mystery wide open.

Police are still trying to identify 33 women whose snapshots were found in Lonnie Franklin Jr.’s home after his arrest.

The images were part of a chilling discovery of nearly 1,000 photos of women or teenage girls – many nude and some who appeared to be unconscious or dead – hidden in Franklin’s house. The collection included photographs of several victims, which leads police and prosecutors to believe Franklin left behind many more.

Detective Daryn Dupree said Franklin is one of the most prolific killers and could have killed as many as 25 women from the late 1970s until his arrest in 2010. That includes the period of 1988 to 2002 when police originally thought the killer took a break – an apparent hiatus that helped coin his nickname.

“I don’t think he stopped because he was getting away with it,” Dupree said. “I think he slowed down, but I don’t think that big gap was as much as we thought it was.”

Franklin, 63, was sentenced to die Wednesday for murdering nine women and a 15-year-old girl in South Los Angeles. Prosecutors outlined evidence of three additional slayings he wasn’t charged with and two other women who went missing and they suspect he killed.

The student identification card of Ayellah Marshall, 18, who disappeared in 2006, was found in Franklin’s garage along with the Nevada driver’s license of Rolenia Morris, 29, who was last seen in 2005. Two snapshots of Morris were found in his photo collection.

Defense attorney Seymour Amster wouldn’t comment on the possibility that his client was involved in other killings. Franklin denied any role in the killings to investigators, and his attorneys had suggested a mystery man was the real killer.

Many of the slayings occurred when U.S. cities were reeling from the crack cocaine epidemic. Franklin targeted young women in the poor area where he lived. Some were drug users who had turned to prostitution in desperation to support their addiction.

“Back then, you’d drive down the street and girls would be trying to jump in your car,” said Dupree, who grew up in the area and witnessed the crack’s effect.

Several other serial killers prowled the area, preying on the same type of victims, who were often sexually assaulted and then dumped in alleys, parks or trash bins.

The killings were believed to be the work of one man dubbed the “Southside Slayer,” though several culprits were later arrested and charged with additional crimes as DNA evidence became more sophisticated.

Only subscribers are eligible to post comments. Please subscribe or to participate in the conversation. Here’s why.

Use the form below to reset your password. When you've submitted your account email, we will send an email with a reset code.