The nurses tried to stop Douglas Kennedy because there had been no order for the baby's release "and I felt there was a security risk," said the witness, Anna Lane.
She said Kennedy told her he didn't need permission.
Kennedy went on trial Monday in Mount Kisco Town Court on charges of harassment and child endangerment. He calls the charges absurd. He says he was just taking the baby, 2-day-old Anthony Boru Kennedy, for some fresh air outside Northern Westchester Hospital.
But nurses testified that would have been very irregular. Angela Adamo said that when Kennedy approached the nurses' station with his request, she tried to dissuade him because it "didn't seem to make much sense to me."
She also said the baby, in a hat and blanket, wasn't appropriately dressed for a January evening.
Kennedy, the baby cradled in his right arm, was not persuaded and moved to the elevator and stairwell, where Lane and another nurse, Carrie Luciano, tried to block the way, Lane testified.
"He grabbed my left hand ... and twisted my arm," Lane said. "He kicked Carrie and she went flying in one direction and he went in the other direction."
The prosecution played choppy time-lapse surveillance video for Judge John Donohue, who is hearing the case without a jury. The video showed Luciano falling to the floor near the elevator but did not show what caused her fall.
Lane broke down during her testimony and on cross-examination said recounting the incident was traumatic. But Kennedy's lawyer, Robert Gottlieb, pointed out that she had gone on NBC's "Today" show in February, "with a heck of a lot more people watching than are in this courtroom" to talk about it.
He also got Lane to say she is contemplating a lawsuit, reading from her lawyer's settlement offer to Kennedy, which was rejected.
The witnesses testified about a flurry of alarms that were set off during the incident. One blared when Kennedy allegedly took a security band off the baby boy. Two hospital-wide alarms - "code purple" and "code pink" - were called in to declare a disorderly situation and a missing baby.
Defense lawyer Celia Gordon said the "code pink" was inappropriate because it's meant for baby abductions. Nurse Angela Adamo said she ordered the "code pink" when she heard someone say, "He's taking the baby." But she also testified that she never thought Kennedy would fail to return with the infant.
In her opening statement, Gordon said Kennedy was acting on instinct rather than intent when he kicked at Lane.
But prosecutor Amy Puerto said Kennedy did not stop until he encountered a security guard on a stairwell. She alleged he said to the guard, "Do you know who I am?"
The hospital's security chief, Eric Hartmann, testified that he called Mount Kisco police when he heard about the incident. On cross-examination, he acknowledged that he did not have much information about what had happened and told police it was "some kind of custody thing."
Kennedy's wife, Molly, came to court with him on Monday. The couple issued a statement in February that said, "Our simple desire to take our son outside for fresh air has been warped into a charge of child endangerment."
Kennedy is the 10th of 11 children of Robert and Ethel Kennedy. His father was assassinated in 1968. President John F. Kennedy, his uncle, was assassinated in 1963.
Kennedy's arrest was the beginning of a difficult year for the Kennedys in New York. His sister-in-law, Mary Kennedy, hanged herself in May in Bedford. His sister, Kerry Kennedy, has pleaded not guilty to drug-impaired driving after an accident on Interstate 684.
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