Scott County Circuit clerk Karen Boehm said 30-year-old Timothy Brown of Georgetown also pleaded guilty Friday to knowing abuse and neglect of an adult, theft by deception, tampering with physical evidence and abuse of a corpse.
A call to Brown's attorney, Joe Fooks, was not immediately returned.
Police found the remains of 31-year-old Penny Brown wrapped up in quilts and blankets in the car last September. Her body was so decomposed the state medical examiner's office couldn't determine a cause of death.
Police say Penny Brown's body may have been in her brother's apartment for up to two years.