After eating the sandwich, Murphy ordered the woman to open the safe and took $198.50 before ordering her to the back of the store, prosecutors said.
The woman testified at Murphy's trial but did not attend Friday's sentencing.
Murphy declined to speak inside or outside of court.
His attorney told the judge Murphy was physically and sexually abused as a boy and spent the better part of his youth in foster homes.
According to prosecutors and court documents, Murphy began committing crimes when he was 12.
He was convicted of rape at 14 and kidnapping at 19, and has spent the majority of his life incarcerated.
Lavenue said Murphy is a “menace to society” who has not shown any remorse for his crime.
“His victim was an innocent young lady doing the best she could,” Lavenue said.
“She certainly didn't deserve any of the things that happened to her.”