Police have said little about what evidence exists in the case, but University of Utah law professor Daniel Medwed said the lack of a body would make it difficult, but not impossible, to file a murder charge.
"You basically need to have a mountain of circumstantial evidence," Medwed said.
That circumstantial evidence would have to show the person is dead, was murdered and who did it. But a murder case with no body creates an obvious counterargument for the defendant.
"I could envision a defense attorney here saying: 'Well ... we don't have a body. We don't even know that she's dead,' " Medwed said.
West Valley City police Chief Buzz Nielsen said last week police are still waiting for laboratory testing of ashes discovered by cadaver dogs during the Topaz Mountain search that may contain human remains, and they are continuing to sort through a trailer full of evidence taken from the Puyallup home.
No other searches are planned, but Nielsen remains confident the case will be solved.
"We're going to get there," he said.
Utah police and prosecutors have filed murder charges without a body before. The last was that of victim Joyce Yost and defendant Douglas Lovell. In 1985, Lovell was charged with raping Yost, but she disappeared 10 days before she was to testify at trial.
Prosecutors didn't charge Lovell with Yost's murder until 1992. Lovell's wife testified that he hated Yost for accusing him of rape and broke into Yost's South Ogden home, murdered her and buried her near Snowbasin resort. After pleading guilty to murder, Lovell took police to where he said he buried Yost, but her body has never been found. A judge sentenced Lovell to death, but in 2010, the Utah Supreme Court said Lovell should have been better informed of his rights and allowed Lovell to withdraw his guilty plea. A new trial date has not been scheduled.
Prosecutors in Denver last year charged a man with murdering a business partner even though they didn't have the victim's body. Police found a crime scene in which they found evidence of a murder.
A year after the charges were filed, a person walking a dog found the victim's body along Interstate 70 near Cisco, Utah. A trial is scheduled for February.
There's no indication West Valley City police have a witness like in the Yost murder or have found a crime scene like that in the Denver case.
Josh Powell, who has not responded to media interview requests since his father was arrested in Washington on unrelated voyeurism charges in September, has previously said he had nothing to do with his wife's disappearance and that she ran away.
Medwed commended West Valley City police and Salt Lake County prosecutors for taking their time with the Powell investigation.
"Even if the public might be anxious for some developments, I think it's always good for the investigation to proceed as thoroughly and careful as possible," Medwed said.
Nielsen declined to say what information sent his officers to the desert locations this summer, but detectives continue to investigation tips and leads.
"Every one of those searches, there was a reason we went out there," Nielsen said.
About the case
Josh Powell has said he last saw his wife Dec. 6, 2009, as he left her at their West Valley City home and took their sons, then ages 2 and 4, on a late-night camping trip to Simpson Springs in the family's blue minivan. A neighbor reported Susan Powell missing the next day.
The only person of interest in the case police have publicly named, Josh Powell has denied any role in his wife's disappearance. Susan Powell's parents, Chuck and Judy Cox, have accused her husband of being involved in her disappearance and pointed to the couple's rocky marriage.