Michael Bever's murder trial is entering its third week Monday.
He's accused of stabbing his parents and three siblings to death in their Broken Arrow home almost three years ago.
It's possible Robert Bever, who is serving time for the murders right now, could testify this week in his brother's trial.
So far, the jury has heard from one of the surviving sisters, now 16 years old, who testified she was the first one attacked in her family.
"That young lady did an extraordinary job surviving. She's solely responsible not only for her life but for the life of her little sister," said Tulsa County DA Steve Kunzweiler.
Crime scene investigators, nurses, and firefighters have also taken the stand.
It's been an emotional trial so far, with tears in the courtroom as jurors saw pictures of the victims at the crime scene with several of them surrounded by a pool of blood.
Prosecutors also showed the jury a 6-inch straight blade police say was found on Michael when he was arrested.
This week, the jury could hear from Michael's older brother Robert, who pleaded guilty and was sentenced to life without parole for the crimes.
He's back in the Tulsa County Jail for the trial.
"We'll see when the state rests. We'll kind of have to wait and see," said Michael’s Attorney Corbin Brewster.
Kunzweiler is trying to prove Michael committed the crimes with his older brother Robert, but, the defense is trying to show Michael was hardly involved at all, and that it was Robert's doing.
"The role of one in a conjoined crime is just as important as the role of the other," said Kunzweiler. "Robert Bever's involvement, in this case, is very critical to the entire story that's being told."
One thing the jury won't see is the autopsy photos.
The judge said that's because the cause of the five deaths is not in question and the pictures would only inflame the jury.
Attorneys said they hope the trial will wrap up by the end of this week.
News On 6’s Taylor Newcomb will be in the courtroom Monday morning.