Rachael Martin, from Kesh, and her 33-year-old former lover, Barry McCarney, from Trillick, are on trial at Dungannon Crown Court on charges relating to the death of baby Millie Martin in Enniskillen almost three years ago.
The jury of nine men and three women were told that McCarney, who denies murder, is also accused of sexually penetrating the infant girl with a part of his body, either a finger or erect penis, between December 8 and 11, 2009.
He is also charged with unlawfully and maliciously causing the child grievous bodily harm between November and December 2009, and her death by an unlawful act on December 11.
Martin is accused of failing to protect her daughter from the unlawful act that caused her death, and wilfully neglecting her in a manner likely to cause her unnecessary suffering, between September 1, 2009, and December 12, 2009.
Prosecuting counsel, Mr. Ciaran Murphy QC, claimed that the brain and other injuries which led to Millie's death, according to the medical evidence, must have been caused a short time before her lifeless and limp body was rushed to the Erne Hospital by McCarney as Martin was out buying him a KitKat.
He told the jury Rachael Martin was the child's mother and primary carer and as such, given the medical and other evidence, she should have seen or have been aware of the injuries being inflicted on her infant daughter. She was responsible, or ought to have been responsible, for keeping her out of danger.
The lawyer said it was the prosecution case that "Rachael Martin wilfully closed her eye to what she knew, or ought to have known" was happening and "wilfully neglected Millie Martin".
Mr. Murphy said the injuries first began to materialise after Millie's first birthday in September 2009, around the time when Martin first took up with McCarney, who moved into her semi-detatched home at Glebe Park in Enniskillen.
He told the jury it was the prosecution case the injuries suffered by the toddler "were too significant, too severe and too many" for her mother not to have noticed them and she must have "known very well that this child was being abused".
However, the lawyer added that "for whatever reason", maybe her love for McCarney, something stopped her from doing anything to protect Millie, either by speaking out or taking her out of harms way.
In all the circumstances, although it was a matter for the jury, Mr. Murphy declared, had Martin taken steps to protect her daughter from McCarney, it was ultimately the prosecution case: "this child would not have died".
The lawyer said she was initially questioned as a potential witness, but eventually was arrested and interviewed the following September, during which she described her relationship with McCarney as "good ..... they never had arguments or anything like that".
She told police that on that Thursday, December 9, she picked McCarney up from work and he offered to mind Millie, but she refused.
Martin said she only left Millie for five minutes, to go and buy McCarney a bar of chocolate, and returned to find the house empty. Later she got a call from McCarney to say he'd taken Millie to hospital.
While she claimed she had no idea how Millie's ribs got fractured, she did say the child "bruised easily". Martin also claimed that McCarney had told her about bumps on the child's head.
However, she maintained that while Millie appeared "drowsy" on the day she died, she had "picked up around evening" and had played with a "burger box".
Martin also claimed that she never saw anything wrong or around Millie's genital area, and in essence, if she had found any injuries or bruising on Millie "she would have done something about it".
Earlier Mr. Murphy claimed that both Martin and McCarney were alone with Millie, and "nothing untoward" happened to her prior to her mother going to a shop five minutes away to buy chocolate, and immediately before she was rushed to hospital.
Mr. Murphy said if the medical evidence was right, then the only person capable of having an opportunity of "committing the fatal act" was McCarney.
The lawyer told the jury to look at his demeanour at the hospital and of going home and changing his bloodstained clothing.
McCarney's account of trying to revive Millie before taking her to a neighbour's home to run her to hospital were "not consistent with the level of violent injury suffered by this child".
Mr. Murphy further claimed that McCarney had failed to "adequately" account for Millie's state when taken to hospital.
When first asked about the sexual injuries found on Millie's groin area, McCarney claimed that: "I know absolutely nothing about that" and denied harming Millie in anyway and that he was "shocked and sick" at the injuries she'd suffered.
McCarney also told police that he'd never even changed Millie's nappy and that while he couldn't explain the injuries he was "not the only person who had excess to Millie".
Mr. Murphy said that McCarney was initially arrested on suspicion of sexually abusing baby Millie. However, following her death he was questioned over a three-day period up to December 14, accused of her murder. He claimed that on the day he'd rushed Millie to hospital he'd finished work early because he'd felt unwell. Later that evening, while Martin went to the shops, he'd gone and checked on the little girl, whom he claimed had earlier looked "really sleepy".
McCarney allegedly told police he found the child gasping, and that when she stopped, he thought something must be caught in her throat, so he put his fingers down her mouth in an effort to clear the supposed blockage.
When she didn't respond, McCarney in his own words said he put her on the floor and started "hitting her...you know...on her back".
At one stage he gave the youngster mouth-to-mouth, and pumped her chest a few times, before rushing next door to a neighbour's house with Millie in his arms. As they drove to the hospital, McCarney claimed he continued to try and revive her and "poked her in the chest" until they reached the Erne Hospital.
Mr. Murphy said that as they drove to the hospital, McCarney's neighbour ordered him to stop "slapping the child".
The prosecution lawyer said that it was the opinion of State Pathologist, Professor Jack Crane, having reviewed the evidence of a number of specialist consultants who'd treated Millie, and later examined her remains, that the youngster died from head injuries.
The pathologist reported that there was "unequivocal evidence" of severe impact injury to the back of the skull, with other possible injuries to the front and side of the head.
"The severity of the injuries was such that it is likely to have resulted in rapid loss of consciousness.....shortly before going to the hospital .....pointing inexorably to Barry McCarney as the person who had this child in his care shortly before going to hospital," the court heard.
Mr. Murphy said that Professor Crane detailed other injuries, including fading bruising to the chest, stomach, elbow with healing fractures to six right ribs, and five on the left, "caused by the chest being forcibly grabbed or squeezed".
Some of these fractures were up to four weeks old, while others had possibly been sustained within 10 days of her unfortunate death.
The lawyer also revealed that Professor Crane was also of the "opinion......Millie Martin had been recently sexually assaulted".
Mr. Murphy revealed that one expert who'd examined the fractures to Millie's ribs, claimed the force required to cause such injuries was akin to something "like a road traffic accident".
The English-based Scottish consultant reported that the Millie's rib injuries were non-accidental and that since it was difficult to injure the ribs of a 15-month-old infant, they must have been caused in Millie's case by "severe gripping or squeezing ....beyond even rough handling" of the youngster.
The trial continues, and is expected to last eight weeks.