Ashiqur Rahman has pleaded not guilty to manslaughter and aggravated assault in the July 27, 2009 death of seven-week-old Aurora Breakthrough.
The 26-year-old took the stand in his defence before the Supreme Court of Nova Scotia, and repeatedly denied the allegations of his former girlfriend Jane Gomes.
Gomes has testified that she saw Rahman hold the legs and arms of the baby and shake her when the girl cried during a diaper change in July 2009.
But Raham denied that happened, saying Gomes passed him the dirty diapers during the changes while Gomes held the child's legs.
"I never held the legs and hands together," he said.
He said sometimes he held the baby's hands if Aurora was hitting herself in the face when her arms flailed about during a change.
Gomes pleaded guilty last year for failing to provide the necessities of life and received a conditional discharge with six months of probation. She agreed to testify at Rahman's trial as part of an agreement with the Crown.
Last month, she told the court she saw Rahman slap the baby after they argued about a hospital bill incurred while she and Aurora were at the IWK Health Centre in Halifax.
Rahman said he didn't strike the baby and never argued with Gomes about the bill because they both understood the provincial health agency would pay the fees.
"She had already contacted MSI (Nova Scotia's public health plan)," he testified. "We didn't have a conversation about that at all. She knew what to do."
During her testimony, Gomes said Rahman was distant from the child and appeared more interested in his computer science business projects than in being a father. She also said Rahman argued violently with her and struck her on several occasions.
But Rahman, a former computer science student at Acadia University, said that isn't true.
He agreed he had almost no involvement in the child's care in the first three weeks of her life because that was what the couple decided together.
"Jane and I had a discussion and she suggested and I agreed that she would carry out the care of Aurora and I would do the (computer) work," he said.
He said his focus at the time was testing software for an online gambling website he'd developed.
Rahman also said he only had disagreements with Gomes on two occasions, calling them "differences of opinion," adding that he never physically harmed her.
Gomes has also alleged that on June 29, 2009, she had gone grocery shopping for several hours in the evening and left Rahman alone with Aurora. She said when she returned, Rahman apologized to her for slapping the baby due to his frustration with her crying.
Rahman denied this Tuesday, saying it was unlikely Gomes would have left him alone in June because she was still breastfeeding the baby.
Rahman said he worried about his daughter at times because she appeared not to react to stimulus such as music or smiles.
However, he said Gomes told him she'd asked about this at a local health clinic and she was told that wasn't unusual.
Under cross-examination by Crown lawyer Mark Hareema, Rahman said he had loved Gomes, wanted to have a baby with her and planned to marry her.
Hareema questioned that, asking Rahman why computer records seized by police showed that three weeks after Aurora was born he received a confirmation of registration for a matchmaking website.
Rahman replied that he registered on the website because he believed it was about relationships in general, and when he realized it was for finding a new mate, he stopped using it.
The trial has heard a neuropathologist testify that Aurora had tears that left gaps in her brain tissue that occurred more than two weeks before her death.
The case resumes Wednesday.