At first, a young Irish tourist thought a Manhattan investment banker was joking around when he barged naked into the bathroom where she was changing, but in seconds she was on the floor being raped, she testified Tuesday.

The woman, now 22, returned from Ireland to testify against Jason Lee, 38, who is on trial charged with first-degree rape in Suffolk County Court. Stifling both tears and shaky hands, she described how a night of drinking in East Hampton ended with a sudden, violent attack.

The woman said she came to the United States on a student work visa and worked at a frozen yogurt shop in Myrtle Beach, South Carolina. She and a friend then traveled to New York City.

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"We wanted to see this big city that everyone talked about," she said during questioning by Assistant District Attorney Kerriann Kelly in a Riverhead courtroom filled with lawyers, local and Irish reporters and other spectators. District Attorney Thomas Spota watched from the front row.

Then they took a train to Montauk, where the woman's brother was working at the Surf Lodge. On the night of Aug. 19, 2013, she said, they met at the Surf Lodge and then took a taxi to the Georgica Restaurant and Lounge in Wainscott.

"It was very fancy," she said. "Too fancy for us."

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After struggling with the concept of bottle service, they shared some Absolut vodka. She said she had six or seven drinks before some other men invited her and her friend to their table. She identified Lee as one of those men, her face crumpling as she did so.

Lee's group drove them to the house Lee was renting, she said. She and her friend were astounded to find a swimming pool in the backyard, saying such a thing is unheard of in Ireland.

She and her friend stripped to their bras and underwear and jumped in the pool, while Lee took all his clothes off and ran around in the yard, she said.

The night included drinking champagne out of a bottle and eating microwaved pizza until the woman said her brother told her it was time to go. She said she got her dress and went to a bathroom to change out of the clothes she had borrowed after swimming.

She said she had just finished changing when the door swung open to reveal Lee, naked again. She tried to close the door, but he shoved it open, she said. She tripped backward onto the floor and he pinned her hands to the floor, she said.

"I didn't really understand what was happening," she said. She told him to get off, she said.

He muffled her with the back of his hand, told her to shut up and began to rape her, she said.

"With every ounce of strength I had inside of me, I pulled my knee up and hit him," she said, adding that she got him in the groin. He left and she took off the dress she had just put on.

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"Why?" Kelly asked.

"Because it was disgusting," the woman replied, sobbing.

In his opening statement, defense attorney Andrew Lankler of Manhattan said the sexual encounter was consensual.

But during his cross-examination of the woman, Lankler did not ask if she consented to sex, focusing instead on how much she drank that night and on variations in her accounts of what happened. For example, she told East Hampton police Lee came to the bathroom before she changed into her dress, not after.

"I've had a year and half to process what happened," the woman explained. "I was extremely stressed that day."