Nancy Guthrie update: 'Whistleblower' speaks out and claims to know who is to blame

In the Nancy Guthrie case, criticism of investigators continues to mount, especially against Pima County Sheriff Chris Nanos.

As six months have passed and no suspect has been arrested, a whistleblower has come forward and placed the blame squarely on the senior officer.

His name is Sergeant Aaron Cross.

He is the president of the Pima County Deputies Organization, a union representing sheriff's deputies.

Given his background and insider knowledge of the department, Cross told TMZ that Pima County made several botched decisions early in the case.

Together, he claimed, these decisions plagued the investigation to find Nancy.

One of them, Cross said, was handing the case to less-experienced officers.

For example, he alleged the lead detective on the case was unqualified for the investigation.

He claimed he had never worked a homicide before but still “was placed in there nearly immediately."

Just three years before, Cross alleged, the detective had been promoted and noted that he “very rapidly went inside from patrol and then was assigned to homicide.”

He continued, “Command, for whatever reason, decided that even though he hadn’t been in homicide before, he was the right person for that unit."

According to Cross, the decision hampered Nancy's disapperance, with responsibility squarely falling on Nanos, who is himself facing a $176 million lawsuit over alleged incompetence in a different case.

Nancy, meanwhile, has not been heard from since Feb. 1 when she went missing from her home near Tucson, Arizona.