As Illinois becomes the fourth and most populous state to give illegal immigrants permission to drive, nagging concerns remain about whether there are enough safeguards to avoid the identity fraud and other pitfalls other states faced.

Democratic Gov. Pat Quinn signed Illinois' measure into law Sunday in Chicago. Backers, including Quinn, Chicago Mayor Rahm Emanuel and some of the state's top Republicans, tout it as a public-safety measure. They argue that required facial recognition technology is reliable enough to prevent fraud.