Madeleine Stowe's character was originally a poet, but Stowe asked if the script could be changed to make her a musician. Stowe then learned how to play the violin for the role.
Madeleine Stowe visited doctors at UCLA to study blindness. Aidan Quinn and James Remar spent time with members of the Chicago Police Department, and the line "We will solve no crime before there's overtime" was provided by some of the officers.
Emma's dog, Ralph, is a trained guide dog. These animals are trained to focus on assisting their owners, specifically to ignore distractions in their environment and to obey their masters instantly. Yet Ralph barks when Emma walks down the stairs, he pulls away from her in the car park to investigate something and he chases the man ignoring Emma's calls to come back. These behaviours are totally out of character for a guide dog.
Thomas Ridgely: [giving Hallstrom hell outside of police station after Emma ran off under his protection]
She's acting this way because of YOU! Now I'm going into that station, dragging her back to her apartment, and I'm going to handcuff her to the fucking bannister!