Police have new information in the murder investigation of an Aiken teacher.

Ann Smith's co-workers found her stabbed to death in her home on April 25. She taught at Kennedy Middle School.

Now investigators are saying some of her family members are preventing them from finding her killer.

It's an investigation that started out with too many unanswered questions: Who would want to kill Kennedy Middle School teacher Ann Smith? Was it someone she knew?

Detectives say there were no signs that someone broke in her house.

Now almost a month after her death investigators say the people they need the most stopped helping out with the investigation.

"Early on in the investigation, you're asking all types of questions. We wanted to know who her associates were. It was very early on that some family members hired attorneys," said Lt. David Turno, Aiken Public Safety.

Smith's estranged husband Wilson and her 16-year-old son both hired attorneys. Smith's other son, stopped returning phone calls to the police. Investigators say family members did offer DNA samples during the initial investigation, but they refused to take a polygraph test.

"This crime deserves to be solved. We need the cooperation of her family to let us know who she was associated with, so we can solve it. Their lack of cooperation makes it difficult on us,” said Lt. Turno.

NBC Augusta has also learned Ann Smith filed papers with the Aiken County family court in November 2007.

In the court documents Smith made claims of adultery and physical abuse in her marriage. She also told the court she wanted a divorce. But no official divorce papers were filed.

Police say these court documents are just part of their investigation. Their focus is getting a killer off the streets before someone else becomes a target.

"We have a concern for the offender. The people that might be close to him or her, they could be in danger,” said Lt. Turno.

Detectives want to stress Smith's estranged husband and son are not suspects in her murder, but they have not been ruled out. Investigators say they have cleared Smith's daughter and many of her friends and co-workers. SLED is still processing evidence.