Barry McCarney, who is 33 and from Woodview Crescent, Trillick, denies not only murdering Millie, but also sexually and physically abusing her, while the toddler's 27-year-old mother, Rachael Martin, from Main Street, Kesh, denies wilfully neglecting and allowing the death of her daughter.
During a police interview McCarney told the police: "All I can tell youse is the truth about what happened and I have been over it and over it and over it and over it again with youse and I have told you nothing but the truth."
He said he was there "to help" and that: "I want the person who did this arrested.
"They should be punished for it," he stated.
Later he repeated that he "wanted to find out who done this to Millie, I want to find out", but that he had not "accidentally" caused any injury to the infant whilst in his arms when being driven to the Erne Hospital.
The court also heard that as police continually pressed him and detailed Millie's injuries, McCarney maintained that he was "sick and disgusted when you read out stuff like that there".
During further interviews McCarney told police that when he found the child in her cot the "only thing that was going through my head was, keep her alive, keep .......keep alive .....get her to the hospital".
McCarney said that was all he did for Millie and that he "did my best for that child".
He also maintained that he had never noticed any bruising on the child, although he was not "saying they were not there.... I didn't check for them".
Later he added that because he had neither bathed nor changed Millie's nappy "I never saw those bruises, I know nothing about those bruises"
McCarney claimed that when he first started dating Rachael he was "completely mad about Millie, mad about her, I played with her .....done loads of stuff with her".
He also told police that he often spoilt the child behind her mother's back as Rachael would "get upset" at him spoiling Millie.
"I spoilt her now and then, more than anybody else would," McCarney claimed, before adding: "before I came she wasn't allowed sweets or, biscuits, or nothing like that".
McCarney, who agreed with detectives that he was "a wee but softer" with Millie, said that he would "give her a lot of that type of stuff ......I'd be giving her lots of biscuits, crisps, chocolate, stuff like that".
The trial continues.