Mount Kisco, New York (CNN) -- Three nurses saw it this way -- it was a gut reaction that led to a kick in the guts.
The suburban New York maternity ward nurses testified Tuesday they were simply trying to protect Douglas Kennedy's infant, whose head was bobbing as his father tried to take him outside the hospital, allegedly without permission. That's when Kennedy kicked one of them and twisted the arm of another, they testified.
It was the second day of Kennedy's criminal trial on misdemeanor charges of harassment and child endangerment resulting from what happened in January at Northern Westchester Hospital in Mount Kisco, about 40 miles north of New York City.
One of the nurses, Cari Luciano, said that as Kennedy tried to get past the nurses and into the stairwell, his infant's head was being jostled, unsupported, in his arms. She testified that she instinctively reached out to steady it when Kennedy kicked her squarely in the pelvis.
Nurse Marian Williams said she saw Kennedy kick Luciano with "such force" that it knocked her off her feet.
The third nurse, Anna Lane, testified Kennedy twisted her arm off the stairwell door as he tried to leave.
"The baby was bouncing around in Mr. Kennedy's arms," she testified, explaining why the three nurses tried to intervene.
Prosecutors say the nurses were simply following hospital protocol set up in newborns' interests when they tried to keep infant Bo from being taken out of the hospital. Not only did Kennedy not back down, prosecutors say, but he fought back.
Kennedy removed the baby's electronic security bracelet and laid it on the counter before he headed for the elevators, prosecutors say. The nurses were trying to enforce hospital rules when they stopped him from using the elevators, and that's when he headed for the stairs, they say.
Once he kicked the nurse, Kennedy only got as far as the next landing when hospital security stopped him, Lane testified Monday.
Defense lawyer Celia Gordon suggested Monday that Kennedy was calm during the situation, and that things only deteriorated because of Lane. It was Kennedy's instinct, not Lane's, to protect his baby from being ripped from his arms, she said in her opening statement.
Kennedy's attorney has previously said the nurses initially agreed to let Kennedy take the baby outside.
But their attorney, Elliot Taub, has said neither Lane nor Luciano recognized Kennedy as the child's father.
Williams, who witnessed the alleged assault, said she couldn't understand why Kennedy would want to take his newborn outside for "fresh air" at 7 or 7:30 in the evening.
"I didn't understand why he tried to do it," she testified.
There is a host of procedures before a baby can be discharged, Lane said. A supervisor needs to approve it, forms need to be signed and family members, including the infant's mother, need to agree. None of the procedures was followed, she said.
Lane testified she asked Kennedy to identify his baby, Bo, by his hospital bracelet, and to go back to his mother so she could match the names. She said she asked him to put Bo in a bassinet and go back to the room. He refused both times, she said.
Infant alarm systems are standard in many hospitals as a way to protect the babies' safety. Newborns wear electronic bracelets that cause alarms to sound and doors to be locked if the baby is taken out of the ward, and newborns are often released only to the mother, whose bracelet must match the baby's.
The defense noted Lane and Luciano hired a personal injury lawyer before any charges were brought, suggesting it was intended to put pressure on the police and district attorney to charge Kennedy. That would be leverage for a future civil suit, according to the defense.
The defense also questioned why, if recounting her story was so emotionally difficult, Luciano laid it out on NBC's "Today Show" soon afterward.
"I felt that my reputation was being defamed, like I had done something wrong or horrible," Luciano explained Tuesday. She said she wanted "more clarification to know I did the right thing. I did my job. I did what was best for the baby."
Douglas Kennedy is the youngest son of the late Robert F. Kennedy, who was the younger brother of slain President John F. Kennedy and had served as U.S. attorney general and U.S. senator. He was assassinated in 1968 while campaigning for the Democratic presidential nomination.
The trial is set to continue Wednesday.