Hieatt, 47, stared blankly at the table in front of him for much of the interview with Detective Daniel Egen - shown at his murder trial in Auckland today - his silence only broken by his occasional mumbled monosyllabic answers to the police questions.
After about 30 minutes he broke down in tears and said "I killed her" but told the detective he had nothing more to say than that.
The remaining half an hour of the two hour interview will be shown tomorrow.
Upon his arrest, Hieatt told Mr Egen he had choked his girlfriend Nuttidar Vaikaew, 48, a Thai sex worker, to death on April 17 last year.
Her badly decomposed body was found nearly a month later in a bed in her Auckland apartment.
Hieatt lived in the apartment during this time.
The court also heard evidence today from Pranom Khotngao, who was flown from Thailand to give evidence at the trial.
She told the court she met Hieatt on an online dating website and he visited her three times in Thailand.
She said that he spoke to her via an online messaging service when he was back in Auckland and told her he had killed Ms Vaikaew after they had had a big fight.
She said Hieatt's message said: "She made me crazy. I think she wanted to die and made me do it."
Ms Khotngao said she was worried Hieatt would kill himself so she tried to calm him down but he said "she's dead, nobody can fix that".
"I don't think I'll be able to see you again, I should have stayed with you, I'm sorry," he told her.
The Crown is expected to finish calling evidence tomorrow and Hieatt himself will take the stand.
