Izett then placed his daughter's body face down in the Little Waihi estuary mudflats and weighed her down with two large rocks, and the toddler drowned, Pollett said.
Ager, who gave birth to her and Izett's son on March 18, 2019, told the court on Monday it was the first time Nevaeh has been left in her former partner's sole care.
Izett has also denied charges of wounding with intent to caused grievous bodily harm, injuring with intent to injure and assault relating to two civilians and a police officer.
These offences are alleged to have been committed between March 18 and 21, 2019.
Yesterday, the jury heard evidence from several Little Waihi residents and regular visitors who gave similar accounts about Izett's "erratic" and "odd" behaviour having escalating in the three months leading up to Nevaeh's death.
Kirsten Smith said Izett's behaviour was sometimes "odd" and a "little erratic" and used to see him out in the estuary sparring using a pole more than once by himself.
Smith said about 7.30 am on March 21, 2019, she heard a commotion in the water and saw Izett again being a "little erratic" out on the mudflats near this pole.
Izett was yelling loudly his behaviour got "louder, then softer, then louder" again and it was like he was having an "argument" but with himself.
Smith said she then saw him kneeling down beside the pole but still yelling something.
"I don't distinctively remember whole sentences but it just sounded like ... he was half yelling and half crying maybe."
Izett stayed kneeling down in calf-high water doing this for some time, she said.
Smith agreed with defence lawyer Julie-Anne Kincade QC, that it was fair to say Izett's odd and erratic behaviour had "ramped up" in early 2019.
Judith Parker, who lives in Tio Pl, said Izett's "odd behaviour" included him yelling and swearing, chanting and cursing, often while out in the estuary close to his house.
Parker said about 9.30am on March 21, 2019 - the day Nevaeh's body was found -
she was picking beans in her garden and heard Izett out in the estuary.
"I heard Aaron splashing around in the water, yelling and screaming and waving a white um, like a Māori carving and cursing the Pākehās, and it was f this and f that."
However, she said this was the sort of behaviour Izett quite frequently displayed.
"The next thing I heard was splashing and saw Aaron running across the other side of the estuary with nothing on and blowing a whistle."
Parker said she rang the police and while on the phone she could see a naked Izett running "very fast" down the road towards his house, with his carving and the whistle.
When police arrived Izett told the two officers to f-off and he was "going at them" with a pitchfork, then ran back into the estuary.
Parker said the officers told Izett he could keep his whistle, but he needed to come out of the water and talk to them, but he refused to co-operate.
She said about 4.30pm the day before, Izett yelled out to her and asked whether she had a match or lighter and noted he was "dressed up nicely".
"Aaron had a white plastic-like beer jug and my husband also saw it and he thought it looked like petrol. It certainly didn't look like beer. "
Parker said Izett's odd behaviours started not long after he moved to Tio Pl.
She said Izett would often be out in the estuary near a big pole, and hitting it with a belt or something else, and chanting and cursing Pākehā.
"A lot of it was just gibberish, you couldn't really understand it.
"But you always heard 'f***** Pākehās, and he'd whack the pole and then he'd run out further and then come back to the pole ... just normal behaviour for him."
Defence lawyer Nicholas Chisnall has told the jury that Izett does not deny killing Nevaeh but the defence rejected the Crown case that his client had murderous intent.
Chisnall said Izett should be found not guilty by reason of insanity at the time he committed the unlawful acts.
The trial continues.
