The mother and her boyfriend have been charged with murder in the January beating death of 4-year-old Tahjir Smith, Montgomery County authorities announced Friday.

Lisa Smith, 19, and Keiff King, 26, both of Willow Grove, had been held on attempted murder and other charges since their arrests after the boy's death.

A forensic pathologist, Ian Hood, who had been awaiting test results following a Jan. 23 autopsy, determined on March 30 that Tahjir died of multiple blunt injuries, thermal injuries and shock, and ruled the death a homicide, District Attorney Kevin R. Steele said.

Smith and King were each charged Wednesday with first-degree murder, Steele said.

Officials have said Smith and King beat the child as punishment after he spilled his cereal the morning of Jan. 22 and stuttered a confession to his mother.

According to charging documents, the couple struck Tahjir's head, torso, and bare buttocks with their hands and a shoe. When the child became unresponsive, they placed him in the shower under hot water, officials said.

The boy was dead by the time medics, who had been summoned to the home for a respiratory emergency, arrived, police said.

Smith and King are being held without bail. A preliminary hearing is set for April 18.