The Middlesex District Attorney's office announced on Tuesday that it will not charge the driver who struck and killed Shira B. Palmer-Sherman '02 while she was crossing Eliot St. in Brattle Square on Dec. 17.

"At this time, our case is closed," said Benjamin Fitzpatrick, the assistant spokesperson for the district attorney's office. "No charges have or will be brought in connection with this case."

"After a thorough investigation by the Cambridge Police Department (CPD) we were presented with no information that criminal conduct occurred," he added.

CPD officers took the driver into custody shortly after the accident on an outstanding warrant. He was later released on bail.

The driver told the police that he had not seen Palmer-Sherman as she crossed the street near Charlie's Kitchen. When he felt the car hit something, he slowed down and pulled over to the side of the road to see what had happened.

In the initial stages of their investigation, CPD officers also attempted to contact the driver of a red car seen at the scene of the accident, but they later determined that this car did not contribute to the accident.

"The other vehicle was not involved," said Frank D. Pasquarello, spokesperson for CPD. "It pulled over to assist, and after the occupants assisted they drove off. When they read the story [in local papers], they came forward and explained."

A lack of witnesses to the accident, which occurred at about 8 p.m., severely hampered the lengthy investigation, conducted by both CPD and the Mass. State Police.