The federal judge who will decide whether to block Arizona's sweeping new immigration law has dealt with the realities of the state's porous border for nearly 10 years.

Susan Bolton sentenced a Mexican smuggler to 16 years in prison for leading 14 illegal immigrants to their death in the broiling Arizona desert.

She decided in 2002 that Border Patrol officials had legal immunity and couldn't be sued for their part in a 1997 immigrant roundup that led to 430 arrests and drew complaints that Hispanics who were U.S. citizens were harassed because of their appearance.

Now Bolton, a former state court judge appointed to the federal bench in 2000 by President Bill Clinton, finds herself in the thick of the biggest question in immigration in years: Whether states frustrated with federal border efforts can dig into the fight against illegal immigration.

"I think she would be the best judge to have on this type of case," said retired Maricopa County Superior Court Judge Kenneth Fields, describing Bolton as a down-the-middle jurist with a knack for handling complex cases while possessing rich judicial experience that includes stints in criminal, civil, family, juvenile and drug courts.

Arizona's new law requires police, while enforcing other laws, to question a person's immigration status if officers have a reasonable suspicion that the person is in the country illegally. Seven lawsuits have been filed challenging the measure, which is set to take effect July 29 unless Bolton blocks it.