In 2008, Daniel Sanders was pulled over by police for driving erratically. A shovel and his mother's body were in the trunk.
On Tuesday, he pleaded guilty to manslaughter and felony evidence tampering for drowning her and attempting to hide the body.
Prosecutors said they lacked the evidence to convict the 20-year-old of murder, so they offered him a deal, which he accepted.
Assistant Boone County Prosecutor Andrew Scholz was worried that the prosecution didn't have answers to some questions that could be asked during the trial, especially about the drowning of Sanders' mother. Investigators still suspect a family connection in the drowning, and the initial indictment said that Sanders didn't act alone.
In January, Sanders' lawyer, Christopher Slusher, filed a motion that said Sanders asked for an attorney when he was pulled over, making the vehicle search unconstitutional and the discovery of the body inadmissible.
The agreement was made before Boone County Circuit Judge Gary Oxenhandler was able to decide on the motion.
A 15-year sentence and a four-year sentence were recommended by the prosecution and will be served consecutively. Scholz said he preferred to give Sanders a 19-year sentence than risk a trial.
Did prosecutors made the right decision in offering Sanders a plea deal? Is 19 years a fair sentence for the case?