Sen. Russell Pearce, R-Mesa, introduced the bill, which passed the Senate in February and is now being debated by the House.

According to the legislature, there are an estimated 460,000 illegal immigrants living in Arizona.

The bill would make the first offense of illegal immigration punishable by up to six months in jail, and the second offense punishable by one and a half to three years in prison. The bill will require illegal immigrants to pay a $500 fine as well as any jail fees.

Opponents have criticized the bill because many immigrants don't have money to pay the fees in the first place.

Tombstone Marshal Larry Talvy opposes the bill for different reasons. Talvy is worried that the bill is only being pushed to lessen the workload of federal law enforcement and add to the workload of local and state law enforcement.

"If illegal immigration becomes a criminal act, we'll be handling all the arrests, putting illegals in jail, awaiting arraignment, prosecution and deportation," said Talvy. "It alleviates the workload of feds, and the state and local departments are already limited in resources. They need to find smarter ways to handle illegal immigration."

Talvy sees one benefit: those illegal immigrants who are caught will be more willing to enter plea agreements by giving information about individuals involved with smuggling across the border.

Arizona law enforcement officials and Arizona Prosecuting Attorneys' Advisory Council (APAAC) worry that criminalizing the presence of illegal immigrants will hinder cooperation from victims and witnesses in criminal cases.

"Our biggest fear with this bill is that victims and witnesses who are illegal immigrants will now no longer cooperate with us if we are obliged by law to report them as illegal," said APAAC Executive Director Paul Ahler.

"We could be dealing with serious crimes: homicides, robberies and assaults. It will be more difficult to put together cases if illegal immigrants are afraid to cooperate with law enforcement and prosecutors," Ahler said.

With additional cases to handle and with a rise in the number of people jailed because of convictions, there's little doubt that it would prove costly, but Ahler couldn't make a prediction as to what the costs will actually be.

He added, "If it's the law, we'll support it."

Democratic Rep. Kyrsten Sinema of the 15th District is a highly vocal opponent of the bill.

She says the mandate for local police to enforce federal immigration laws "will have an unbelievably horrible effect on community policing. It will prevent people from calling police officers to report crimes.

"The mandate will force police officers to look into the citizenship status of every single witness of a crime; these undocumented witnesses will be deported for doing a good thing."

Pearce said the bill would help combat violence because many illegal immigrants are criminals. He also said that officers wouldn't be required to turn over all immigrants, though the bill reads otherwise.

Border Action Network (BAN), an Arizona organization formed in 1999 to protect immigrant rights, is fighting the bill.

Hilary Tone, a spokeswoman for BAN, says the group worries about the bill's potential costs.

"It applies a one-size-fits-all approach to law enforcement and local governance. It takes local decision-making, discretion and flexibility away from local agencies and officials," she said.

BAN brought letters to the governor and held a demonstration outside her office Wednesday urging her to veto the bill.

According to BAN, it has gathered more than 8,200 letters addressed to the legislature.

Former Gov. Janet Napolitano repeatedly vetoed bills attempting to criminalize illegal immigration.Gov. Jan Brewer won't comment on the pending legislation, but both supporters and opponents of the bill are confident she will approve it.

Tone said BAN expects the bill to pass, but the group is doing everything possible to oppose it.