Authorities say Amanda and Grant Hayes killed Laura Ackerson, who was the mother of Grant's oldest children, and dismembered her body before pouring acid on it and dumping it in a Texas creek in 2011.
Investigators believe the couple dismembered Ackerson's body in their hall bathroom and later cleaned the apartment with bleach, trying to get rid of any evidence left behind.
During their investigation, they found bath mats and a shower curtain they believe were missing from the Hayes bathroom inside a dumpster at the couple's apartment complex. They also found areas of the carpet that appeared to have bleach stains and a spot on a bed comforter that tested positive as likely being blood.
However on Friday, a crime lab analyst told jurors that the bleach had destroyed any evidence of blood.
One of the few things that could have placed Ackerson at the Hayes' apartment was a strand of her hair, but because she had visited there before and since her children lived there and could have transferred it, officials said it doesn't mean much.
"I have no way to tell how long a hair has been there, or when it was deposited," SBI Crime Lab Analyst Jennifer Remy said. "All I can tell that it is there, and because the timing of the event was of importance and when the hair was deposited, would have been of importance because I can't tell that there was no need to examine it."
Amanda Hayes defense claims she is not a murderer and she did not know of Ackerson's death until after she and Grant arrived at her sister's house in Texas - where she claims Grant threatened her if she didn't help with disposing of the body.
Much of Friday's evidence pointed at Grant - not Amanda. But one word could have hurt the defense - if the jury caught it.
On the witness stand, the attorney who represented Ackerson in her battle to regain custody of her two young boys from Grant took the stand. He described Ackerson's fear that Hayes might go so far as to kill her. In describing the conflict, lawyer John Sargeant used the word "they."
"Mr. Hayes knew the [mental] evaluation was not going his way. So she was afraid that they might do something to her to try to gain advantage in the custody case," said Sargeant.
Grant is serving a life sentence for murdering Ackerson. If convicted, Amanda could face the same sentence.