A 31-year-old woman accused of shoving an immigrant from India to his death in front of a New York subway train because she believed he was Muslim laughed and smiled during a court hearing where she was ordered to undergo a psychiatric evaluation.

Erika Menendez, 31, was charged on Saturday night with murder as a hate crime after she told police she spontaneously pushed Sunando Sen, according to prosecutors.

"There is no reason. I just pushed him in front of the train because I thought it would be cool," she said, according to the Queens district attorney's office.

She laughed so hard during her arraignment in Queens criminal court that Judge Gia Morris told her lawyer: "You're going to have to have your client stop laughing."

Defence attorney Dietrich Epperson said her behaviour in court was no different from how she had been acting, and said his client didn't really think the proceedings were funny, according to Newsday.

He represented her for the arraignment only and had no further comment.

Menendez was held without bail and ordered to have a mental health exam.

Queens prosecutors said she pushed the 46-year-old Mr Sen to his death because she blamed "Muslims, Hindus and Egyptians" for the September 11, 2001, terrorist attacks.

"I pushed a Muslim off the train tracks because I hate Hindus and Muslims - ever since 2001 when they put down the twin towers I've been beating them up," Ms Menendez told police, according to the district attorney's office.

Friends and co-workers said Mr Sen, a native of Calcutta, was Hindu. He had lived in Queens for decades and was a graphic designer and copy shop owner.

Mr Sen was standing on an elevated platform of the Number Seven train that travels between Manhattan and Queens when he was shoved from behind as the train entered the station.

Witnesses told police a woman had been mumbling to herself and was sitting on a bench behind Mr Sen until the train pulled in, then shoved him from behind. She then fled.

Police released a sketch and surveillance footage of a woman running from the subway station.

Menendez was arrested after a passer-by saw her on the street and thought she looked like the wanted suspect.

Witnesses identified her in a line-up and she was questioned by police, when she implicated herself, according to police and prosecutors.

Angel Luis Santiago, who used to work at the Queens building where Menendez's mother and stepfather live, said he was shocked by her arrest.

"It surprised me what she did," he said. "She never acted that way."

Menendez's next court appearance is scheduled for January 14.