The 2008 disappearance of 15-year-old Yasmin Acree sparked a massive police investigation that sent detectives on hundreds of leads, including false sightings that stretched from her tough West Side neighborhood to Michigan and New York City.

But Tribune reporters recently uncovered a piece of potential evidence that hadn't been turned up by police: a diary Yasmin hid in her bedroom.

In it, Yasmin twice mentioned a 35-year-old man who had lived for several months in a separate second-floor apartment at her two-flat.

"I miss Tyrell …," Yasmin wrote.

Yasmin was referring to Jimmie Terrell Smith, who had moved into her building after serving more than 10 years for attempted murder.

Described in court records as a brutal predator, Smith is now in Cook County Jail awaiting trial on charges of raping five females, including two 14-year-olds he is alleged to have kidnapped. Smith had shown an interest in Yasmin and had contact with her after he moved out of her two-flat, including at a family friend's house shortly before she vanished, according to Tribune interviews.

In three recent jailhouse interviews, Smith told the Tribune he had vital information about Yasmin's disappearance.

"I know what happened to her," Smith said, although he did not admit any direct involvement in Yasmin's vanishing.

Smith claimed he also was responsible for four uncharged homicides. But for now, Smith said, he wasn't going to say what he knew. "I'd be putting my head in a noose."

Smith's statements may be the fabrications of a career criminal facing the possibility of years behind bars, and Yasmin's diary entries may simply reflect her private teenage fantasies.

But over the last 18 months, detectives have twice brought Smith from jail to question him about Yasmin, including once for more than 30 hours. And earlier this month, based on information uncovered by the Tribune, police obtained a warrant to search a now-empty South Side home where Smith had lived on and off with a girlfriend in 2008 and 2009.

For 90 minutes eight officers moved in and out of the frame house in the rain on the evening of March 4. An evidence photographer's strobe lit the home from within and officers' flashlight beams swept the backyard as they combed slowly for evidence amid the downpour. Police left with four evidence bags.

The Tribune's reporting on Yasmin's disappearance not only sheds light on Smith's contacts with her, but adds new dimension to her life and the often-criticized police investigation into the case.

Police failed to uncover potential leads, even beyond the diary discovered by reporters. It took nearly a year and a half for detectives to learn that Smith had lived in the building's second-floor apartment.

Yasmin's diary, as well as Tribune interviews with more than a dozen relatives and renters in Yasmin's two-flat and hundreds of pages of government records, shows the fragile girl was in many ways left unprotected by the adults in her life, including child welfare authorities.

A caseworker made monthly visits to Yasmin's home until May 2006 but apparently wasn't aware that Smith or his father, who also had a criminal record, lived in the building owned by her adoptive mother, Rose Mae Starnes.

And Yasmin wasn't getting effective help to address the dominant feature of her life: a history of childhood sex abuse that left her with low self-esteem and little sense of boundaries. She repeatedly sought out inappropriate contact with others, opened herself to advances and engaged in behavior that made her a high risk for exploitation and flight, records and interviews show.

"My sister was a troubled child. You have to tell the whole truth or people can't understand the story," said her 20-year-old brother, Damarcus Acree, who spoke at length with the Tribune.

Starnes said she loved Yasmin and did everything she could to keep her safe. But in a futile effort to rein in Yasmin's troubling behavior, Starnes said she sometimes whipped the girl with a belt, or confined her to the home's dank basement because "I didn't want people finding out about Yasmin, and I didn't want Yasmin doing things to other kids."