Arizona Sheriff Joe Arpaio, the self-described toughest sheriff in America, has added a taxpayer-funded deputy to his volunteer team in Hawaii determined to investigate "inconsistencies" in President Barack Obama's birth certificate.

The newest member of Arpaio's volunteer Hawaiian "Cold Case Posse," deputy Mike Zollo, has joined the team in part because the investigation has "progressed," according to Arpaio, and because of "security issues."

"It's one deputy, so what? We have security issues, too, that I can't got into," Arpaio said to the Arizona Republic. "For six months we were not spending any money. When you're doing investigations sometimes things change, you put more resources into it."

Zollo, who is part of the sheriff's threats unit, will continue to work on other cases as while working on the Obama investigation, but his actual mission in Hawaii is still not entirely clear.

"He's not going to make any arrests," Arpaio told the Republic. "I didn't say we're going to keep using him. We're not going to use him constantly. He's not assigned to it. For this trip I feel it's important to have a deputy there. He's just a liaison to give advice if needed. He's not doing anything. The posse's been doing the research. I'm not going to say what other trips they've been taking but they haven't had a deputy with them."

The "birther movement" --  which questions the validity of Obama's birth certificate and eligibility to be president — gained steam after Arpaio launched the investigation last year. The sheriff claims it was started at the request of 250 Tea Party members in Surprise, Arizona. Thus far, Arpaio's Hawaiian posse has spent close to $40,000 of donated money, according to the Republic.

Over two months ago, the Maricopa County Sheriff held a press conference to proclaim the revival of the so-called "birther" controversy at the conclusion of the six-month investigation that found the president’s birth certificate, which shows he was born in Hawaii, may have been a "computer-generated forgery," according to Arpaio. His team also found irregularities with Obama's Selective Service card.

The Obama birth certificate controversy has been widely debunked but remains alive in the eyes of some conservatives including, most recently, Donald Trump, who spoke on the issue while entertaining a bid for the presidency last year.  

The Obama campaign has since posted a copy of the "certification of live birth" on the White House website.

Recently,  the U.S. Department of Justice officially filed a lawsuit against Arpaio, claiming his deputies ethnically profiled Latinos. The sheriff has said the investigation was a politically motivated attack by the Obama administration.

Arpaio has built his reputation on jailing inmates in tents and dressing them in pink underwear. He has campaigned as a tough-on-crime candidate who aggressively pushed for a stronger role for local police to confront illegal immigration, launching 20 patrols looking for undocumented immigrants since January 2008, according to the Associated Press.

The revival of the birther controversy can be traced back to Arizona's legislature as well as its controversial sheriff.

Arizona officials endorsed a proposal in March that required presidential candidates to swear that they meet the qualifications of the nation's highest office. The proposal would have made candidates complete a new form asking eligibility questions, including whether they are natural-born U.S. citizens. The proposal was vetoed by Republican Gov. Jan Brewer, who called the measure "a bridge too far."

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