OLYMPIA, Wash. (AP) -- The parents of a missing Utah mother pushed Friday for changes in Washington state laws on custody cases, saying proposed legislation might have prevented the killing of their two grandchildren.

Chuck and Judy Cox testified before a state Senate committee considering a bill that would restrict or block visitation rights for someone who is the subject of a murder investigation.

They told lawmakers the legislation could have changed the course of the case involving their missing daughter, Susan Powell, whose husband Josh Powell killed himself and their young kids during a parental visit.

"Most likely, they would have officially named Josh Powell a suspect in order to afford Charlie and Braden more protection," Chuck Cox said, referring to the grandchildren. The grandparents had custody of the two children.

Authorities in Utah had long been eyeing Josh Powell in the 2009 disappearance of his wife. Powell killed his children last year when they arrived at his home for a supervised visit.

Utah investigators never publicly declared Powell a suspect but treated him as one privately.

The proposed law in Washington would allow people involved in custody cases to demand information from law enforcement that might be relevant to decisions on visitation matters.

Republican Sen. Pam Roach, who is sponsoring the proposed bill, said it provides more tools for judges to restrict visitation. She noted that some visitations can be limited to just once a month in a public place -- not in a private home.

"We need more parameters around our current law to give us a wake-up call and bring us back to common sense," Roach said.

Rick Bartholomew, who testified on behalf of the Washington State Bar Association, said he supported the idea behind the bill but not the implementation.

He expressed concern that some investigations are left open for long periods of time and ultimately lead to the exoneration of parents, which could mean parents would be separated from their kids for extended periods of time, even if they did nothing wrong.

Bartholomew also said the rule requiring law enforcement to turn over details of an investigation during a custody case could harm the murder probe.

The suspect in a murder case could use the tool in order to get a glimpse inside that investigation, he said.

A committee of senators hearing the bill did not take a vote on the measure Friday.