In El Mirage alone, where Arpaio's office was providing contract police services, officials discovered at least 32 reported child molestations with victims as young as 2 in which the sheriff's office failed to follow through, even though suspects were known in all but six cases.
Many of the victims were children of undocumented immigrants, said a retired El Mirage police official who reviewed the files.
The botched sex-crimes investigations have served as an embarrassment to an office whose sheriff is the self-described "America's Toughest Sheriff" and a national hero to conservatives on the immigration issue.
Arpaio's office refused several requests over a period of months to answer questions about the investigations and declined a public records request for an internal affairs report, citing potential disciplinary actions.
Brian Sands, a top sheriff's official who is in charge of the potential discipline of any responsible employees, declined to say why they weren't investigated. "There are policy violations that have occurred here," Sands said. "It's obvious, but I can't comment on who or what."
Sands said officers had subsequently moved to clear up inadequately investigated sex-crimes in El Mirage and elsewhere in the county. He said leads were worked if they existed, and cases were closed if there was no further evidence.
Arpaio's office was under contract to provide police services in El Mirage as the city struggled with its then-dysfunctional department. After the contract ended and El Mirage was re-establishing its own police operation, the city spent a year sifting through incomplete casework.
El Mirage Detective Jerry Laird, who reviewed some the investigations, learned from a summary of 50 to 75 cases files he picked up from Arpaio's office that an overwhelming majority of them hadn't been worked. That meant there were no follow-up reports, no collection of additional forensic evidence and zero effort made after the initial report of the crime was taken.
"I think that at some point prior to the contract [for police services] running out, they put their feet on the desk, and that was that," Laird said.
Arpaio acknowledged his office had completed an internal probe into the inadequate investigations, but said, "I don't think it's right to get into it until we get to the bottom of this and see if there's disciplinary action against any employees."