One of the arguments fueling the passage of Arizona's immigration law -- the growing threat of border violence – has come under scrutiny as statistics show that the state may not be as dangerous as supporters of the law say.

While it's tough to determine just how dangerous the state is, what is certain is the notion that Phoenix has become the world's No. 2 kidnapping capital has been based on stats taken out of context, if not totally blown out of proportion, criminal data experts say.

"Kidnappings are very complicated particularly because they often cross jurisdiction boundaries and when you get into these kinds of things, that's when the reliability of the states kind of goes out the window," Paul Souza, of the University of Nevada, Las Vegas, told Fox News.

Crime statistics gathered by the FBI show a steady decrease in violent crime over the last three years – in all major metro areas in Arizona.

In Phoenix, for example, violent crime went down over 16 percent in the last year.

Authors of the contested Arizona immigration law say many of those here illegally have left this year – the reason for the drop in crime.

"We have had a significant reduction over 100,000 illegal aliens that have left this state," said Arizona state Sen. Russell Pearce. "We've had a corresponding relationship with the reduction in violent crimes."

Validating Phoenix as the kidnapping capital of the country is virtually impossible. Many cities across the country do not gather the number of kidnappings that occur within their jurisdiction at all.

Supporters of the Arizona law helped guide its passage in April by arguing it would compensate for the federal government's failure to secure the border and fix the immigration system. Opponents say the law promotes racial profiling and is unconstitutional.

A federal judge last month put most of the law on hold before it went into effect July 29, including on-the-spot police checks of suspected illegal immigrants. A federal appeals court will hold a hearing in November on Arizona's challenge to the ruling.

Arizona Gov. Jan Brewer has vowed to take the case "all the way to the Supreme Court if necessary."

Fox News' Casey Stegall contributed to this report.