West Valley police said the focus shifted to Michael C. Powell after Josh Powell killed the couple's two boys and himself in a deliberately set house fire 15 months ago.
Police held a news conference Monday to say they are closing the active investigation of Susan Powell's disappearance, citing a lack of leads coupled with Michael C. Powell's own suicide only months ago.
Police released the case file, which includes details that have been kept under wraps since Powell vanished in 2009. Police have said they would reopen the Susan Powell case if they get new information.
Her father, Chuck Cox, believed Josh Powell poisoned his wife's pancakes before she was taken from the couple's house.
"The question is, where did he put her and will we find her before she does die?" Cox wrote in an email to Utah authorities, according to the police file. "One possibility is that she is still alive, but we need to find her before she does die, if the poison was not a fatal dose, she may ... be found."
Police based their suspicion of Michael C. Powell's involvement partly on a car he left at an Oregon junkyard only weeks after Susan Powell disappeared. The junkyard is about 200 miles from a forest outside Salem, Ore., where authorities searched last week, looking for a body. The search turned up nothing, and police said they ran out of clues.
Deputy West Valley Police Chief Mike Powell — no relation — said authorities believe Josh Powell killed his wife, and that his brother later got involved in a cover-up. Michael C. Powell denied any wrongdoing while under investigation.
It wasn't until last August that Utah police discovered Michael Powell's Ford Taurus at the junkyard outside Pendleton, Ore. DNA recovered from the upholstery inside the car's trunk proved inconclusive, they said.
The Powell brothers used sophisticated computer encryption to communicate, according to West Valley City Deputy Chief Phil Quinlan. Investigators have been unable to decipher that encrypted communication, he said.
Investigators said they focused on the brother last year, when Josh Powell changed his insurance policy to list Michael Powell as a primary beneficiary, rather than his wife or children.
Michael Powell, an ardent supporter of Josh Powell, killed himself Feb. 11 by leaping from a parking garage in Minneapolis. He was interviewed numerous times last year after investigators determined he had sold his car for salvage value — a discovery that came nearly two years after Susan Powell's disappearance. Officials said he offered evasive answers about why he got rid of the car and how he had used it in the weeks after her disappearance.
His suicide left investigators without any person of interest in the case. While authorities believe the brothers were responsible for Susan Powell's disappearance, they said repeatedly Monday that they never had enough evidence to bring charges.
"This is a circumstantial case, yes," Quinlan said. His fellow deputy chief, Mike Powell, added, "We didn't have a body. We don't have a crime scene."
Susan Powell was reported missing more than three years ago after failing to show up for work. Her husband, Josh, maintained his innocence and said he had taken the couple's young boys on a midnight camping trip in freezing temperatures the night she was last seen.
Josh Powell eventually returned to the couple's hometown of Puyallup, where he got caught up in a battle with Susan Powell's parents for custody of the boys, 7-year-old Charlie and 5-year-old Braden.
On Feb. 5, 2012, he locked a social worker out of a rental home at the start of a supervised visit, attacked the boys with a hatchet and set the house afire. All three were killed in the blaze.
Days earlier, a court had ordered Josh Powell to undergo an intensive psychosexual evaluation in the custody dispute.
Josh Powell was never charged in his wife's disappearance, but unsealed documents say authorities found drops of Susan Powell's blood on a floor next to a sofa that appeared to have been recently cleaned, with two fans set up to blow on it. Investigators also found life insurance policies on Susan Powell and determined that Josh Powell had filed paperwork to withdraw her retirement account money about 10 days after her disappearance.
Susan Powell, then 28, was last seen Dec. 6, 2009.
"We have searched high and low for what happened to Susan Cox Powell," West Valley Mayor Mike Winder said. "What happened to Susan that night?"
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