The backyard mechanic accused of being the "Grim Sleeper" serial killer pleaded not guilty Monday to murdering 10 women and trying to kill one more person over the course of two decades.

The pleas were entered by an attorney for defendant Lonnie Franklin Jr., who spoke only to answer procedural questions in Superior Court.

Prosecutors have not decided if they will seek the death penalty.

Franklin, 57, was wearing an orange prison jumpsuit with his hands shackled to his waist.

About 30 family members and friends of victims attended the hearing. Some were in tears as they left court.

Franklin is accused of killing the women from 1985 to 1988 and from 2002 to 2007. The 14-year pause led to the nickname "Grim Sleeper."

Outside the courthouse, attorney Louisa Pensanti, a private attorney who is representing Franklin for free, said she would assemble a team of lawyers to look through more than 8,000 pages of documents provided by prosecutors.

Lawyers will focus on DNA evidence against Franklin, which Pensanti said was "not as cut and dry" as authorities assert.

All the women were killed within a few miles of Franklin's home in South Los Angeles, where neighbors knew him as a talented backyard mechanic.

Police also have said they suspect Franklin of killing a man who may have discovered he was a killer. Investigators were reviewing more than 30 other cold case files to see if they can tie Franklin to other slayings.

Franklin was arrested in July after his son was arrested and swabbed for DNA. Using a technique known as a familial DNA search, the sample came back as similar to evidence in the serial killings, ultimately leading police to Franklin.

Franklin is due back in court Sept. 14.