As Sharon Flanagan entered the Best Western Parkway Center Inn in Green Tree the evening of July 1, 2012, she was carrying her 2-year-old boy.
Wearing a blue T-shirt, shorts and a red plastic fireman's cap, Steven had his arms wrapped around his mother's neck until she plopped him down on the counter while he ate a lollipop.
"He was happy. He was laughing, and he's playing with his mommy while she checks in," said assistant district attorney Lisa Pellegrini. "And the next time anyone sees Baby Steven, he is facedown in the bathtub, lifeless and unresponsive.
"There's no water in the tub. His little red fire hat is in the tub, and his little Crocs."
Ms. Flanagan, 34, of Inwood, W.Va., is charged with homicide in Steven's death, and her trial began Tuesday before Allegheny County Common Pleas Judge Jeffrey A. Manning.
Ms. Pellegrini told the jury of seven women and five men that the defendant was in the midst of a bitter divorce and killed her son to get back at her husband.
When investigators reviewed Ms. Flanagan's history on her computer, the prosecutor said, they found that she had recently searched online for "leading cause of toddler death," and "why is Casey Anthony so popular."
Ms. Pellegrini is seeking a conviction for first-degree murder.
According to several witnesses who testified, Ms. Flanagan exited her sixth-floor room about 8:30 p.m., and began flailing, clutching her stomach and shouting, "My baby. My baby."
She ran to the lobby, where she repeated the behavior.
But Ms. Pellegrini told the jury during her opening, "She never tells anyone 'my baby is in the bathtub. I don't have a card key.'
"Nobody can figure out what's going on."
People staying in the room adjacent to Ms. Flanagan saw her acting strangely in the hallway and thought from the woman's actions that she might have been having a miscarriage.
"She was screaming and clutching at her stomach like she had been kicked or punched or injured," testified Dominic J. Netti. "She was gasping for breath as she was screaming."
He repeatedly asked her what was wrong, but she didn't answer. Then she got in the elevator and left.
He said it took several minutes, and a security guard in the hotel returned to the room with a card key to open the door. Ms. Flanagan wasn't with her.
Mr. Netti entered the room with security, immediately spotted Steven in the bathtub, lifted him out and started doing CPR until emergency personnel arrived.
The child was taken to the hospital, and as detectives tried to gather information, Ms. Pellegrini said, they found that Ms. Flanagan's statements were inconsistent.
She told detectives she couldn't pull the boy out of the bathtub, but also told them he was able to get in and out by himself. Steven weighed 35 pounds.
Defense attorney Blaine Jones told the jury the boy's death was accidental.
"Forcibly drowning someone is an extremely violent act," Mr. Jones said, noting that Ms. Flanagan's son had no marks on him of any kind.
"There is a distinction between forcibly drowning someone and someone accidentally drowning," he said.
He described his client as soft-spoken and religious -- attending church seven days a week.
As for Steven, Mr. Jones said the boy was "the light of her life."
"He was her everything," he said. "She invested all of her time, energy and love into him."
The attorney said Ms. Flanagan put Steven's swim trunks on so he could play in the bathtub.
"Unfortunately, Sharon's attention was distracted. Before she could do anything, Baby Steven was unresponsive."
Mr. Jones said his client was running through the hotel seeking help.
"It was no act, ladies and gentleman, she was frantic because her son, her world, was unresponsive."
Paula Reed Ward: firstname.lastname@example.org, 412-263-2620 or on Twitter @PaulaReedWard.