The investigation of Hailey Bannister’s December death lasted longer than her life.

Over seven months, Mercer County detectives pored over the texts her parents sent to each other, and a friend, interviewed family members and talked to doctors who treated the 3-month-old before she stopped breathing one day at her Ewing home.

What they found, and alleged in two court documents, was her police officer father abused the girl for most of her brief life, fracturing her skull and ribs and leaving her covered in bruises, all because he wasn’t bonding with his newborn as he’d hoped.

And her mother knew about the abuse and was concerned, but did not report it to authorities or doctors, the documents said.

The fatal injury, detectives said, occurred in later November, likely on the 23rd. Hailey Bannister died on Dec. 11.

Daniel Bannister, 31, is charged with her murder. His wife, Catherine Bannister, 29, faces a charge of endangering the welfare of a child. They entered not-guilty pleas in Superior Court of Mercer County on Thursday afternoon.

Daniel Bannister joined the Ewing Police Department in 2017 and was suspended with pay shortly after her death. That was upgraded to without pay Wednesday, following his arrest, Ewing Police Chief John Stemler said.

Catherine Bannister was a kindergarten teacher at Foundation Academies in Trenton, where she started working in 2014, according to her LinkedIn page. The Foundation board approved extended paid maternity leave for her on Dec. 19, and in May, voted not to renew her contract.

First responders arrived at Bannisters’ residence on Gilmore Road Dec. 5, 2018 when Catherine Bannister called 911 because Hailey was having difficulty breathing. Doctors at Capital Health Regional Medical Center in Hopewell determined the infant had a fractured skull, brain bleed and fractured ribs, according to the probable cause affidavits charging the Bannisters.

Detectives started investigating Hailey’s death that day, Dec. 5.

She was listed in critical condition and later transferred to Robert Wood Johnson Children’s Hospital in New Brunswick. She died there on Dec. 11.

An autopsy ultimately concluded in May that Hailey died from blunt-force trauma to the head. Her wounds revealed ongoing abuse, visible from nine skull fractures, some of which showed signs of healing, leading investigators to determine she had been hit multiple times on different dates, according to the documents. There were also signs she had been shaken, and four ribs fractured weeks before her death.

When investigators initially spoke to her parents, separately, Daniel Bannister told them he was home with Hailey and their 2-year-old son Dec. 5 while his wife was at work. He said he went to check on her after placing her in a bouncer, and found her breathing to be odd and shallow, according to the charging document.

He allegedly said he took her out of the bouncer just as Catherine Bannister came home to breastfeed her. He said his wife called 911 as he attempted CPR on the baby, according to the affidavit.

Daniel Bannister also said his 2-year-old son had accidentally hit the infant in the head on Nov. 22., detectives wrote in the documents.

Catherine Bannister told investigators she had woken up the morning of Dec. 5, fed Hailey and put her in the swing before leaving for work. She told detectives she’d taken Hailey to the doctor several times the week before, even once bringing her daughter to a hospital. Hailey was diagnosed with reflux and given medication, the documents say.

But she also told investigators that Hailey was a cranky baby who cried a lot, and her husband had trouble bonding with the infant, according to the court documents. She had asked him to be gentler with the baby, she told investigators.

Investigators confiscated the couple’s phones, which included texts where Catherine Bannister had repeatedly told her husband she was concerned with how he handled Hailey, that he had left bruises on her face, head and midsection, according to the charging document.

She did not, however, tell doctors about the bruises, according to the document.

In a text from Oct. 4, when Hailey would have been just over a month old, Catherine Bannister confronted Daniel Bannister about bruising around the baby’s mouth that allegedly came from him pressing his finger against her mouth to stop her from crying.

Days later, she texted a friend who worked as a pediatric nurse about Daniel Bannister’s abusive behavior toward their daughter, but asked her not to report it. She told the friend she had told her husband he was “abusive” and couldn’t touch the infant again unless he took a class on early childhood development, according to the charging document.

The friend offered Catherine Bannister and the children a place to stay, urging her to get away from her husband.

On Nov. 1, Catherine Bannister took a photo of bruising on Hailey’s ribs, and sent it to Daniel Bannister while at a doctor’s appointment.

“Hopefully doctor won’t see,” she allegedly texted.

A doctor later pinned the date of Hailey’s fatal head injuries as Nov 23, the day after Thanksgiving. Alleged texts confirmed Daniel Bannister was home alone with the children that morning.

During another doctor’s visit on Nov. 23, Catherine Bannister sent her husband a photo of a bruise on Hailey’s head. “She threw up again, a lot,” she texted him. She suspected her daughter might have a concussion, but did not raise those concerns with pediatricians, according to the affidavit.

Despite her husband’s alleged pleas not to, Catherine Bannister took Hailey back to the doctor the next day. She told medical staff Hailey had vomited after almost every meal, but allegedly did not mention the bruising, her husband’s rough handling of the baby or the concussion possibility.

Catherine Bannister then took the baby to the emergency room, where staff proposed diagnostic testing. The infant’s mother allegedly refused to allow anything other than an ultrasound.

“Omg I just saved her from an iv,” she texted Daniel Bannister. She allegedly texted him she would yell at medical staff who tried to do any further testing.

When interviewed by investigators, family members, including Hailey’s grandparents on each side, said they did not know how the young girl was injured.

A friend of Catherine Bannister’s, Jessica DiPietro, said the charges are a shocking development in the devastating story of Hailey’s death. While the two had caught up mostly on social media in recent years, she described her friend as “sweet” and “down to earth,” saying she always posted photos of her, her husband and her toddler son.

“When Hailey was born, it was the same thing all over again,” she said. “The pictures, she was so proud of being a mom to both of them."

Amanda Hoover can be reached at ahoover@njadvancemedia.com. Follow her on Twitter @amandahoovernj. Find NJ.com on Facebook.

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