CHICAGO | A man who briefly dated a Chicago woman faces first-degree murder charges in her death after investigators found that his cell phone activity conflicted with his alibi, Chicago police officials said.

Reginald Potts Jr., 31, of Chicago, has been charged with first-degree murder, auto theft and robbery in the death of Nailah Franklin, 28, interim Police Superintendent Dana Starks said Saturday.

Before she disappeared, Franklin had complained to police that Potts had telephoned her making threats.

"She was in the process of obtaining an order of protection when she ended up missing," said police Cmdr. Steve Peterson, who called the crime an example of domestic violence. "When it leads to this, it's tragic for everybody."

Franklin's disappearance triggered a frantic search. Family members and volunteers papered the city with fliers, took out a newspaper ad seeking the public's help and launched a Web site.

Her nude, decomposing body was found Sept. 27, eight days after she was reported missing when she didn't show up for a work meeting. She was a pharmaceutical sales representative for Indianapolis-based Eli Lilly.

Days before her body was discovered, her car and some personal items were found near an abandoned building in Hammond, about three miles from where her body was discovered in Calumet City.

Potts is being held at the Cook County Jail and is scheduled for a bond hearing Monday. It was not immediately clear if he has an attorney. He has denied any involvement in Franklin's death.

"What would be the motive for me to do anything to her?" Potts told the Chicago Tribune last month in an interview the newspaper did not publish until Saturday. "It's an unfortunate situation, but it doesn't mean I should be run through the ringer. I had nothing to do with it."

Potts has a criminal record and a history of violent threats, mostly against women, the newspaper reported.

Besides the cell phone records, witnesses contradicted Potts' story about where he was when Franklin vanished, police said Saturday. Police declined to give details on Potts' alibi because their investigation is continuing.

"Mr. Potts tried to win sympathy, portraying himself as the real victim, but investigators were never swayed by his antics," said Deputy Superintendent Hiram Grau.

Police credited the FBI and Franklin's family for their help with the investigation.

"We can't bring Nailah Franklin back to her family and friends, but at least they have the comfort of knowing that her murderer is behind bars," Grau said.

The Cook County medical examiner's office has not released Franklin's cause of death, a spokeswoman said Saturday.