The mother of an infant who died in August 2009 was charged with murder and child abuse Wednesday in Jackson.

Amber Murphy, 31, was arrested Tuesday and arraigned today on one count of first degree premeditated murder, and one count of first degree child abuse. An alternative charge of felony murder is also on the table instead of premeditation.

"There has never been any doubt that this defendant is responsible for the death of this child," said Jackson County Chief Assistant Prosecutor Mark Blumer to Judge Goostrey's court during the arraignment.

Prosecutors say Murphy's 9-month-old son, Seth, died after an intentional blunt force trauma to his head in August 2009.

It's taken almost three years to complete the investigation, but prosecutors and police finally obtained a key piece of evidence in order to arrest Murphy and bring the charges: an eye witness to the incident.

"We believe we have a very good case," said Jackson County Prosecuting Attorney Hank Zavislak. "We'll present the evidence, and we believe the evidence is significant or we wouldn't have moved forward. Now we'll let the system work."

Prosecutors and police aren't revealing much about the witness. They said it's in the best interest of the prosecution to let that information come out later in open court.

Jackson Police and prosecutors met regularly over the past couple of years regarding this case. They didn't want to jeopardize a conviction by bringing charges too soon.

"The important thing is not to do it fast, but to do it right," said Zavislak. "And that's the approach we've taken."

Police say it's been a long road, but they're pleased with the investigation.

"We are in it to see that there is some justice for this victim and for the other relatives related to the victim," said Jackson Police Lt. Chris Simpson.

Murphy has other children, but her parental rights were terminated over a year ago in Jackson Probate Court. She is currently being held without bond. Murphy is next expected in court June 13.