WAKE COUNTY, N.C. – The family of slain Cary, N.C., woman Nancy Cooper filed a motion Thursday afternoon seeking to prove that her husband is mentally unstable and unable to care for the couple's children.

According to the motion, Nancy's parents and twin sister want Brad Cooper to submit to a psychiatric evaluation to find out whether "he is a danger to himself and/or the minor children."

They believe he is mentally unstable and could pose "a substantial risk of bodily harm" to the children if they are left with him unsupervised, the motion said.

Nancy Cooper's parents and twin sister were granted emergency custody of the couple's two daughters last week after telling a judge that Brad Cooper is emotionally unstable.

Attorneys for Brad Cooper filed motions Wednesday asking a judge to release his wife's autopsy report before a custody hearing in Raleigh Friday.

Attorneys for Brad Cooper said he should be given custody of his children because he has not been named a suspect in his wife's murder. In addition, they pointed out that in the couple's separation agreement, Nancy Cooper said Brad was a fit parent and that it was in the best interest of their children to continue to see him.

Kathy Bradley, a family law professor at Duke University, said this custody battle will be challenging because unlike most hearings, this one only involves one parent.

"There's a strong presumption in the parent's favor," Bradley said. "So, for custody to go to someone other than the parent, the court will have to make a determination -- on the record in written findings -- that it is in the best interest of the child and necessary for the child to be with someone other than the parent."

Court documents filed by both parties paint very different pictures of the family's life in Cary, N.C.

Brad said he shared in the daily care of his girls and pointed out that his wife wanted to share custody of the girls with him. But numerous affidavits from Nancy's friends said he was never around and only recently got involved in his daughters' lives.

Bradley said those testimonies will factor into the judge's decision Friday.

"If, in fact, his involvement is a fairly recent development, it may undercut his credibility on that score in terms of what he knows about his own children," Bradley said.

Brad said his daughters have been wrenched from the only stable environment they know and said only he can provide the love and stability they need.

But Nancy's friends said he's not fit to care for them, nor would he be able to provide a stable environment.

The judge's decision tomorrow is not necessarily a final one. Changes in circumstances for either party could result in another custody hearing.

Stay with News 14 Carolina for complete coverage of Friday's proceedings.