The infant was last seen in a car seat in the back seat of Sean Philips' car.
After a two-year investigation Attorney General Bill Schuette decided to file charges in the missing baby case.
New Evidence Uncovered
"New evidence has been discovered which supports a murder charge in this case," Schuette told reporters, but did not reveal any further details.
"This continuing investigation has included review of biological evidence, site visits, and the enlistment of experts from all over the world who are preeminent in their fields," Spaniola said.
Under Michigan law, a charge of "open murder" is punishable by a sentence up to life in prison. But, the charge leaves open the possibility for a jury or a judge to convict the defendant on first-degree murder charges, or other lesser charges.
Convicted of Unlawful Imprisonment
In Michigan, first-degree murder carries a mandatory sentence of life without the possibility of parole.
About three hours after Baby Kate's mother, Ariel Courtland, reported her missing, police found Phillips with the baby's car seat and diaper bag in the trunk of his car. He had the child's balled-up, inside-out clothing inside his pocket, according to police reports.
Phillips was convicted of unlawful imprisonment and is serving 10 to 15 years at the Carson City Correctional Facility.
Authorities said that Phillips took Baby Kate because he was afraid that a paternity test would reveal that he was the father.
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