Together the trust and conservatorship hold about $2.3 million in life insurance proceeds, which are accumulating interest, as well as the Powell home in West Valley City.
Chuck Cox is the conservator for his daughter and used that authority to change the terms of the trust. Terrica and Alina Powell Josh's mother and sister, respectively contend the terms of those agencies were illegally changed to remove them as trustees or beneficiaries.
Their Utah lawyer, Joshua Lee, said being conservator of Susan Powell's estate does not give Cox all the powers that his daughter had, and only Susan Powell had the authority to amend the trust.
"A conservator can amend the trust only in the case of incapacity," Lee told Dever, citing the terms of the trust.
Lee also accused Cox of having a conflict of interest because he used his authority as conservator to make his wife and himself the lone trustees. Lee said Cox is "lining his own pockets."
But Cox's attorney, Ted Buck, told Dever that Cox has an obligation to do what is best for his daughter, and much has changed since the trust was written in 2009.
"Do we think that Susan Powell would have those same priorities after what has happened since 2009?" Buck said. "I don't think so."
Susan Powell, 28, disappeared from her West Valley City home on Dec. 6, 2009.
Her husband, Josh Powell, 35, was investigated by police, but never charged.
Josh Powell killed his two children and himself in 2012 at a home in Graham, Wash.
Cox can only spend trust money to maintain assets, such as paying the property taxes on the West Valley City home. Utah law says Susan Powell can be declared dead after five years, at which time the assets could be distributed.
Cox and his wife Judy traveled from their home in Puyallup, Wash., to attend Tuesday's hearing in Salt Lake City.
In the past, Chuck Cox has said he believes his daughter is dead. On Tuesday, he sounded more optimistic.
"I'm trying to protect my daughter's assets," Chuck Cox told reporters after the hearing, "so when my daughter comes back and she's found there will be something for her to come back to."
Attorneys for the Powells have taken pains to point out that Josh Powell's father, Steve Powell, is not a party in the litigation and does not stand to receive any money. Steve Powell was convicted in 2012 of 14 counts of voyeurism for photographing neighbor girls in various states of undress.