He apparently took his evidence to Maricopa County DA Bill Montgomery,
“From the Sheriff’s Office investigation into suspect documents produced by the White House to date, that investigation has not revealed any evidence that conduct occurred in Maricopa County,” Montgomery writes. “I have discussed this with the Sheriff.”
and
“Specifically, we would need evidence to affirmatively prove that Mr. Obama is not a US citizen,” Montgomery writes. “To date there has been evidence presented leading to speculation that documents have been forged and other documents do not exist. That alone, though, is not sufficient evidence to present to a grand jury and actually have a reasonable likelihood of conviction.”
The forgery definitely occurred in Maricopa County, and for that matter in the State of Arizona. Wherever Obama appeared on the ballot in the USA that required him to post his bona fides, a crime was committed.
The Arizona authorities, under whose aegis Arpaio operates, should have indicted. Instead he got, “To date there has been evidence presented leading to speculation that documents have been forged and other documents do not exist. That alone, though, is not sufficient evidence to present to a grand jury and actually have a reasonable likelihood of conviction.”
Specious reasoning at best. A grand jury itself should have been given the opportunity to pass judgement on that "speculation".