Moncks Corner — A Berkeley County jury watched a video of Roger Anthony Williams at a Summerville Lowe’s buying bags of cement that he allegedly used to conceal his son’s body.

On the third day of his trial, Williams, 31, was seen on the video asking the clerk something. He wanted to know which cement would dry the quickest, according to testimony by his friend Russell Minter, who gave Williams a ride to the store on June 7, 2010.

On the projection screen inside the courtroom, Williams looked calm as he rolled up a new set of cement bags to the store register. Minter said he thought Williams was buying the items for a patio he told him he was building at home.

Instead, later that day Williams stuck his dead son, 2-year-old Rodricus Williams, headfirst into that trash can and covered him with that cement, according to prosecutors.

He was covering up for the death of the toddler, prosecutors said. Williams has been charged with homicide by child abuse.

Dr. Nicholas Batalis, an MUSC pathologist testified about the autopsy performed. The trash can with his body was found by investigators in Orangeburg behind a trailer. Williams’ girlfriend at the time, Grace Trotman, led police to it.

Batalis determined the toddler died of homicidal violence and probable blunt head injury.

Dr. Carol Jenny, an expert physician who deals in child-abuse cases, testified she believes Rodricus Williams died because of repeated head injuries, which led to his eventual collapse.

“There wasn’t one major blow that led to his demise,” she said.

James Falk, Williams’ attorney, argued against Jenny’s testimony because it was based on both medical records and statements from Trotman, which Falk said could be inaccurate.

Trotman pleaded guilty in February to homicide by child abuse for her involvement in the toddler’s death. She told police about their plan to pretend to lose the boy at The Battery in downtown Charleston in July 2010 to conceal his death.

Initially, Williams lied to investigators during his first interview, prosecutors said. In the next interview, less than an hour later, he changed his story once Trotman had told police about the body.

Prosecutors played the audio recording of Williams telling investigators with the Berkeley County Sheriff’s Office that his son had fallen down the stairs in June 2010. He left for work a few days later and received a call from Trotman in a panic that something was wrong with the boy, according to his statement.

Williams urged her not to call an ambulance, he told investigators, because an autopsy would reveal what had happened to the child. Williams told investigators Trotman claimed her 2-year-old daughter had pushed Rodricus into the wall, where he hit his head.

A day earlier in court, Trotman told the jury she’s the one who pushed Rodricus. Roger Williams decided to hide his son’s body, in an attempt to “protect her,” he said. He walked aimlessly around Lowe’s looking for something to put Rodricus’ body in, he told investigators.

He described how he took the concrete-filled trash to Orangeburg and initially thought about dumping it into a pond. Later, he decided to leave it behind a trailer, he said to investigators. He returned to the site a few weeks later to see if it smelled, he said in the recording.

“End of story. God’s honest truth. Nothing more, nothing less,” he told investigators. “I felt obligated. I had to help her. I made a bad move.”

The defense is expected to call its witnesses today. Williams has not decided whether he’ll testify, Falk told the judge.

The jury is expected to begin deliberations this afternoon, Circuit Judge Markley Dennis said.

Follow twitter.com/ncaula for coverage from inside the courtroom.