The 77-year-old's tough stance on immigration and controversial tactics, which include using traffic violations as a means to check the vehicles for anyone he thinks may be an illegal immigrant, has helped him win five consecutive terms as sheriff and catapulted him into the national spotlight.
Since he began his efforts in 2005, Arpaio claims he's arrested around 30,000 illegal immigrants. But America's ultimate law enforcer hasn't been without his share of controversy. Protesters frequently gather outside Arpaio's office.
The Department of Justice has launched an investigation into his methods. And his wings were recently clipped after the government removed his deputies' right to enforce immigration laws on the streets, amidst allegations that he was racially profiling Hispanics. A federal program called 287(g) had enabled Arpaio to enforce immigration law in his county.
Even after his powers were relegated, last month Arpaio announced his 13th illegal immigrant crackdown of the year.
"Nightline" joined Arpaio and Deputy Cory Rengel in their latest highway pursuit.
"We reward people for illegally coming into this country and committing a crime by coming into this country, reward them with jobs," Arpaio said. "I'm not getting into the social aspect, but you do know if you go into the ER many people here [entered] illegally where U.S. citizens have to wait in the back of the line and they get angry about this."
Arpaio says that illegal immigrants are not only criminals, but can bring diseases into the country.
"I have a problem with people crossing this border that have not been checked medically," he said. "I'm very concerned."
Arpaio demurred when asked which ailments illegal immigrants bring into the country, but said, "I don't know -- TB is a big one. We have people in our jail that have TB. Nobody checks them."
The government investigation into his tactics has ticked off Arpaio.
"They do not like me stopping illegal immigrants on the streets, enforcing the laws, they don't like that. They don't like it because stopping people on the streets because they look Hispanic is racial profiling? That's what they say, but we don't do that," he said. "We use minor misdemeanors to catch dope dealers, seize drugs, catch DUIs."
When asked if he considered an illegal immigrant as serious a criminal as a rapist and a murderer, Arpaio demurred.
"Well, I don't know," he said. "I'm not going to compare the type of crime."
And what about criminals like pedophiles? Arpaio said his office is "very serious" about pedophiles, putting many resources towards a county crackdown on pedophilia.
When "Nightline" asked why his office doesn't take aggressive action against pedophiles as it does against illegal immigrants, Arpaio said, "we're clamping down on murders, but nobody will print it, they'll laugh at me."
"[Illegal immigrants,] that's a high interest of this country right now," he added. "And this county and putting resources towards that. I have $1.6 million from the state [legislature] just to do that, not to go after murders, just to go after this specific crime."
Arpaio's Web site claims he "continues to reduce crime with hard-hitting enforcement methods." It also says that his office has "solved several high-profile murder cases, including nine child murders."
The department's performance can be assessed by the percentage of crimes that are solved or cleared per year. Most crimes are cleared either by an arrest or by an "exception," such as where the perpetrator is known to police, but can no longer be apprehended. Clearance by "exception" is supposed to be exceptional. But, in Maricopa County, that's not the case.
In 2006, 75 percent of cases were closed on the basis of exception as opposed to by arrest, according to the Goldwater Institute. In 2008, the Goldwater Institute also reports that only 18 percent of cases were cleared as a result of an arrest, while 82 percent were cleared as a result of exception.
"You know that was a criteria that was not an official type of statistic. That's somewhat how we look at it. It's not an official type statistic...it's just something that our policy is," he said.
"Those figures are misleading because we do solve over 50 percent of our homicides, but it's how you look at it whether it was a husband-wife murder..." Arpaio continued.
Pressed to explain why 82 percent of cases were declared cleared by exception, and if his department was writing cases off instead of reducing crime, Arpaio said his department clears more than 18 percent of cases by arrest.
"We do clear a higher percentage of that. I know that. We clear many, many cases -- not 18 percent," he said.
"Nightline" contacted the Sheriff's department again after the interview and was told that of 7,346 crimes -- only 944 had been cleared by arrest -- which amounts to only 15 percent. The remaining 85 percent were deemed inactive, unfounded or cleared by exception.
We asked Arpaio to address allegations that he's reducing crime on paper, but not in practice. "It's a bad allegation..." he said. "We solve over 50 percent of our murders. I'll put that against any other law enforcement. You're quoting exception and how the FBI clears cases...I got the facts. We have cleared over 50 percent of murders!"
Arpaio argues that he makes prisoners' jail time so painful that they never want to come back. To deal with overflow, around 1,200 inmates are held in "Tent City," the infamous outdoor extension of the jail facility. In blistering Arizona heat, no air conditioning and meticulously rationed meals.
"This is disgusting," one inmate told "Nightline" during a tour of the facility. "I don't care who you are, you should never treat a human being like this. It's wrong. The food we eat is disgusting. We get food that's donated and we don't even know how old it is let alone if it's any good any more. Some people get sick from it. It's more like a concentration camp than anything else."
Arpaio is unapologetic about inmate treatment. "They get 2,500 calories," he said. "It was 3,000 and we knocked it down to 2,500. How many people are on 2,500 calories? I'm not even on 2,500!"
Arpaio then acknowledged that he might consume 2,500 calories per day. "Okay forget about me," he said. "I have to get on a diet. I just gained some weight."
Inmates are also forced to wear old-fashioned black-and-white prison stripes with pink socks, pink underwear and pink sheets. Arpaio notoriously had all the prison underwear dyed pink for better inventory control, according to his Web site, and ordered pink handcuffs to match -- and possibly humiliate.
Another inmate called it all part of his "publicity stunt."
"I think he does it as a publicity stunt," the inmate said. "The pink handcuffs, the reality show...I think he has a taste, a love of the limelight and he should just get an agent and move to Hollywood. No disrespect to you guys, but he brings you guys here and he videotapes us almost like animals."
Arpaio told "Nightline" prison means punishment not pampering.
Thousands have filed lawsuits against Arpaio's department for controversial tactics and treatment. A lawsuit was filed in 1996 after a young man in custody was forced into a restraint chair and died. His family settled for $6 million.
Despite the settlement, Arpaio said he has full confidence in his staff. "Our officers did nothing wrong, there were no criminal charges...My jail officers are great. I have full confidence in my deputies, my staff," he said.
When asked about the millions in settlement pay outs, Arpaio said, "I didn't pay it out, the insurance company paid it out. I would have love for it to go to trial on that case..."
Another man in custody died in a restraint chair and his family was awarded $8.25 million after a surveillance video emerged of 14 guards beating the prisoner and shocking him. Officials were accused of discarding of evidence, including the man's crushed larynx -- an accusation which Arpaio denied.
"That's not true -- the Medical Examiner had control," he said.
Arpaio told "Nightline" he is "not proud of losing anyone."
But before he turned his focus on the border, Arpaio's team of deputies and his so-called volunteer posse were involved in a clampdown on prostitution in 2003. That too wasn't without its difficulties.
The crackdown reportedly backfired because volunteers were seen on video having sexual contact with prostitutes. Arpaio said that was an "erroneous report."
"We went into neighborhood and arrested 40-50 prostitutes. The reasons that the cases were dismissed were political reasons," he said.
The county attorney said it was unable to press charges because volunteers had sexual contact with the people they were supposed to be arresting.
"They were naked because I allowed them to take their clothes off to develop the case -- that's not unusual," Arpaio said. "They had no sex -- one time, one little case, one woman accidentally put her hand on one of our officers -- one time! And that was it...they've done a brilliant job."
"Nightline" pressed Arpaio on his team's "brilliant job." Arpaio said he never lied or denied that volunteers got naked during the crackdown.
When asked if his leadership style encouraged his officers to display patterns of abusive behavior to inmates and others, Arpario said that the allegation was "ridiculous."
"Nightline" went along with Arpaio's team as they looked for illegal immigrants on Interstate 17. Starting at 5 p.m., there were no sign of illegal immigrants until almost 8 when Deputy Carlos was told over the radio that one of his colleagues pulled over a suspicious vehicle. Within minutes, Arpaio is trumpeting his latest catch.
"Eighteen in this vehicle... Just shows you an example of what's going on with illegal immigration," he said.
The vehicle with those suspected of being in the country illegally was pulled over for speeding and an obscured license plate, according to Arpaio.
There's no time for sentiment. The night's bounty -- 16 men and 2 women -- was cuffed and placed in a prison truck. They made it to America, but their journey has come to an abrupt halt.
"I'll tell you one thing. The law says Class 4 felony – that's a pretty serious charge," he said. "We'll see if they knew what they were doing, seeing how much money they paid the smuggler. But you're not supposed to violate the law."
The following morning Arpaio allowed "Nightline" access to his home outside of Phoenix -- a beautiful setting complete with a grand fountain in the backyard.
When asked if he ever wondered if his house was built by construction workers from across the border who have illegally entered the country, Arpaio said, "I would presume that over the years you're probably correct. ..Doesn't bother me at all...I don't know who they are."
And with that, Arpaio returned to what he does best -- chasing the illegals out of town.