It is not known yet if the jury will hear their testimony.
The Ratliff sisters flew into the Triangle over the weekend, one coming from her home in Germany. They are said to be key witnesses in the prosecution's case against Peterson, who is accused of murdering his wife, Kathleen. She was found at the bottom of a staircase in their home; Peterson called it an accidental fall.
Elizabeth Ratliff was Peterson's neighbor when she died 18 years ago in Germany. She was found dead at the bottom of a flight of stairs, just like Kathleen Peterson, and her death recently was declared a homicide.
Her sisters said that coming to Durham "is not a happy time for us. It is a trying time."
Prosecutor Jim Hardin will try to convince Judge Orlando Hudson that the sisters' testimony is relevant to the case against Peterson.
Hudson ruled last week that the jury will hear the testimony of blood-spatter expert Duane Deavers, marking a win for the prosecution.
"It would be in my opinion that it is consistent with the beginning of an assault," Deavers said to Hardin during questioning outside the presence of the jury.