Graves told ABC News that he has known Powell for 15 years and that while he's never seen him get violent with his wife, he can be controlling. The family's commitment lays more with Susan than Joshua right now, he said, but they will continue to support him and hold out hope for Susan's safety.
"For Susan's sake he needs to really open up and talk to everybody," Graves said. "People will listen to him."
Powell's attorney, noted Salt Lake City criminal defense lawyer Scott C. Williams, has denied that his client has been uncooperative and that the only reason Powell is the focus is because of intense pressure on police to solve the case.
Powell failed to show up for a scheduled interview with investigators on Monday, and on Tuesday answered only a handful of detectives' questions, West Valley City Police Capt. Tom McLachlan said.
The captain said that Powell's attorney has made statements that would lead the public to think he's served up his client to police "on a silver platter," but McLachlan said Powell would only answer a few of the investigators' questions.
Powell, he said, "is not fully cooperating, and while he's cooperating at some level it is certainly not the level we would like."
Black noted that at this point, the Powells' neighbors have been more helpful in answering questions than Joshua Powell has.
Forensic psychiatrist and ABC News consultant Dr. Michael Welner told "GMA" that the tough part in a case like Susan Powell's disappearance is separating fact from theories.
When a spouse goes missing, it's only natural to look at their partner, he said, especially around the holidays when tension and financial pressure is at a high.
"When someone vanishes, apparently from her own home with no sign of forced entry ... then naturally the greatest source of conflict comes from the greatest source of intimacy," he said.
Welner said that Joshua Powell could be feeling pressure not just from police, but from his children.
"Even if he isn't compelled to be very involved in the search for finding his mother well, then they're pressuring him, 'Where's mommy?'" Welner said, adding that Powell's lack of cooperation in the face of his children's questioning would be "striking."
The children, he said, could also be credible witnesses, but said police will need to work quickly before they have been "contaminated" by their father or anyone else.
Police obtained a court order to force a DNA sample of Powell Tuesday. McLachlan told ABC News that they secured the court order for Powell's DNA to guarantee they would get it.
DNA samples also have been collected from others, but McLachlan would not elaborate on who they had tested.
Police have been back to the Simpson Springs Campground where Powell told investigators he had taken his young sons on a camping trip in the early morning hours of Dec. 6, they told ABC News, but they could not find any evidence that verified his story.
ABC News has learned that fewer than 20 people visit the remote campground each winter. The temperature the night Powell allegedly took the couple's sons, ages 4 and 2, to the campground was between 10 and 25 degrees, with rain and snow. Powell told police they set out for the trip around 12:30 a.m.
Investigators have been at the Powell home every day since Susan Powell was reported missing Dec. 7, neighbors said. Forensic tests were run in portions of the house, but were not expected back for weeks.