Shayanna Jenkins was granted immunity by the court in February, which means she can be compelled to testify or face time behind bars. There had been a question over whether prosecutors would call Jenkins, who has been in a relationship with Hernandez since high school and is the mother of his 2-year-old daughter.
The two people spoke to the AP on Thursday on condition of anonymity because of a gag order that's in place.
Jenkins has pleaded not guilty to perjury. Prosecutors say she lied to a grand jury investigating the June 17, 2013, killing of Odin Lloyd, who was dating her sister. Lloyd was found shot to death at an industrial park less than a mile from the home that Jenkins and Hernandez share.
Video surveillance viewed by jurors showed Jenkins removing what appeared to be a box from the family's basement the day after the killing. Prosecutors said before the trial they believe the box contained the gun Hernandez used to kill Lloyd, which has never been found.
Jenkins has been coming to court sporadically and sitting behind Hernandez, whispering "I love you," to him at breaks and occasionally joking with him. At times, she has chatted with his lawyers and occasionally passed them notes. She has not appeared in court since March 6. That day, she was not wearing a large diamond engagement ring that would usually be seen on her ring finger.
Associated Press writer Denise Lavoie contributed to this report from Boston.