Both sides said they would call expert witnesses to bolster their arguments.
Deputy Weber County Attorney Letitia Toombs told the six-man, two-woman jury that Morley shook the baby and then slammed him into a changing table, causing the head injuries. She added that Lincoln had broken bones in his arms.
"This is no accident. This is no negligent act," Toombs told the jury. "This is a conscious act of Tisha Morley after a long day. In her frustration ... she slams Lincoln's head down, causing child-abuse homicide."
Defense attorney Jason Widdison, on the other hand, told the panel that Morley did not harm Lincoln.
"The unimaginable happened. Eight-month-old Lincoln Penland suffered injuries that resulted in his death," Widdison said. "But the state's case against Trisha Morley is purely circumstantial. ... Don't believe a single word of it until you have seen all the evidence."
Widdison explained that the only witness was a 3-year-old at the day care who told investigators several days after the incident that Lincoln's brother, Boston, kicked him in the head, yanked on his arms and then slammed the door on his head.
Other children at the day care didn't see anything out of the ordinary, Toombs told the jury. The child's recollection, days after the incident, that Boston did it was fantasy, she said.
"A 3-year-old does not have the strength to cause those injuries," she said, referring to Boston.
In wrenching testimony, Lincoln's mother, Alesha Penland, told the jury that although Lincoln was a small baby, he was healthy and good natured until Feb. 19, 2014. She had dropped her sons off at Morley's house at 7 a.m. It was the third day of Lincoln's stay there. The Penlands had used the day care before, from the time Boston was 3 months to 1 year old.
Alesha Penland said she remembered getting a call from her husband, Christopher Penland, shortly after 5 p.m. that day, telling her to come home quickly because something was wrong with Lincoln. She recalled the young family rushing to McKay Dee Hospital, where a CT scan showed that the boy had a severe skull fracture.
She boarded a medical helicopter with Lincoln to Primary Children's Hospital in Salt Lake City, she said, and then waited for her husband to arrive as doctors worked feverishly on her son.
Ultimately, an MRI showed that Lincoln had no brain activity, she said, choking back tears.
She and her husband called their extended family together so they could say their last goodbyes, Alesha Penland told the jury.
On Feb. 27 at 5:30 p.m., they took their child off life support. He died at 2:30 p.m. on Feb. 28.
Under questioning from Branden Miles, chief criminal deputy attorney for the Weber County attorney's office, Alesha Penland said that Boston was always very kind to his younger brother.
"Boston absolutely adored his brother," she said. "He was nice to Lincoln and very careful with him."
When Roy police Lt. Kevin Smith arrived at Tots & Tykes at 10 p.m. on Feb. 19, 2014, Morley already had prepared a timeline of the day's activities, he testified.
The child began to cry at 9:30 a.m., according to the timeline, and was very fussy. But he ate and went back to sleep. Lincoln ate lunch and had a snack at 3:30 p.m., but he was fussy until 4:30 p.m., when he went to sleep, according to the timeline, Smith testified.
But when Lincoln's father arrived at 5:05 p.m., the child was unresponsive, according to Morley's timeline, however his pupils reacted to light and his breathing was normal.
According to Christopher Penland, Morley told him that Lincoln had vomited on his shirt and bedding that day.
He told the jury that Lincoln felt cool to the touch and that his breathing was shallow.
"[Morley] was saying, What do we do, what do we do?," Christopher recalled. "It was clear he was in distress and we had to get him to the hospital."
The trial, which is scheduled to last two weeks, has been delayed for various reasons, including issues with the defense finding an expert witness.