"As we started kissing each other I felt uncomfortable because she was a bit too old," the teen said.
During the interview he told police he had repeatedly asked Joseph if she was sure she wanted to have sex and she had reassured him.
"This day still haunts me . . . f*** it still comes back," he said.
Though the incident only lasted 10 seconds, according to the boy, he had immediately felt uncomfortable and texted his mother, who had earlier been drinking with Joseph.
The complainant told another of his mentors - a well-known New Zealand celebrity - about what had allegedly happened, prompting a strong reaction.
"F*** he just got angry," the teenager said. "He wanted to punch my head."
The mentor advised the boy to inform Joseph's boss which he eventually did.
On the day in question the defendant and the teen had gone to watch a movie in Manukau.
"There's nothing unusual or inappropriate about this," Crown prosecutor Evan McCaughan said.
"Social workers were encouraged to spend time with the teenagers. What you might think was unusual was what took place next."
He told the jury Joseph put her head on the teen's arm during the screening and rubbed his stomach and chest under his t-shirt despite his protestations.
"I felt like she was going to rape me the way she was touching me . . . I started getting goosebumps," he said.
Afterwards, the pair met the complainant's mother at a restaurant in Mangere and the two women spent the night drinking.
Joseph eventually dropped the boy's mother at her home and the pair allegedly went on to the motel with her blessing.
Defence lawyer Paul Pati yesterday said their case was simple: "No sex or sexual contact occurred."
And he asked the jury to pay close attention to the police interview.
The trial before Judge Gerard Winter is scheduled to end next week.