Mount Kisco , New York ( CNN ) -- No one disputes Douglas Kennedy carried his newborn Bo through the maternity ward of a suburban New York hospital and tried to take the baby outside . Nor is there any question an altercation ensued , involving nurses attempting to keep the baby on the floor . But beyond that , there are only open questions -- especially about why it all happened and who is to blame . Answers finally started to trickle in on Monday , as the trial of the late Robert F. Kennedy 's youngest son began with opening statements and four witnesses taking the stand . Judge John Donahue -- not a jury -- is hearing the case involving misdemeanor charges of harassment and child endangerment . Kicking off the trial , the two sides outlined significantly divergent scenarios of what happened last January at Northern Westchester Hospital . According to Assistant District Attorney Amy Puerto , the nurses were simply following protocol set up in newborns ' interests when they tried to keep baby Bo from leaving the hospital . The infant 's father not only did n't back down , but he fought back -- even twisting one nurse 's arm and kicking another -- the prosecutor said . One of the nurses , Anna Lane , testified Monday that she 'd initially reached in to hold open an elevator door to prevent Kennedy from leaving that way . When he headed toward a stairway door , she ran to it and put her hand on the doorknob . `` I had my hand behind my back and he grabbed my left hand -- which was on the doorknob -- and twisted my arm , '' said Lane . Kennedy raised his foot and kicked another nurse , Cari Luciano , who 'd come to help before entering the stairway , Lane added . But he only got down as far as the next landing , where he was met by security . The defense team was tough on the nurse . Suggesting she had an ulterior motive given Kennedy 's high profile , lawyer Robert Gottlieb questioned a tearful Lane why -- if recounting her story was so emotionally difficult -- she had recounted her version of what happened so soon after the incident on NBC 's `` Today Show . '' Fellow defense lawyer Celia Gordon , in her opening statement , suggested Kennedy was calm and that the situation only deteriorated because of Lane . Any contact with the nurses was due to a father 's instinctual reflex to `` keep someone from ripping his baby from his arms , '' the attorney added . `` ( Lane ) was abrasive , confrontational and changed the entire tone of the discussion ... and wanted to let him know who was in charge of his baby , '' Gordon said . The incident occurred at the hospital in Mount Kisco , located about 40 miles north of New York City and where this week 's trial is taking place . After Kennedy was arraigned in February , his attorney released a statement stating that nurses initially agreed to let him take the baby outside and demanding `` appropriate disciplinary action '' be taken against Lane and Luciano . Timothy Haydock , a doctor at the hospital and longtime family friend who was with Kennedy at the time , asserted in the statement that `` nurses were the only aggressors . '' But neither nurse recognized Kennedy as the child 's father and intended to protect the baby , who apparently had not been discharged , according to Elliot Taub , the attorney for both nurses . They were trying to enforce hospital rules , he said . The hospital , in New York 's Westchester County , issued its own statement in February supporting its nurses . `` At Northern Westchester Hospital , patient safety is our priority and we completely support the actions of our nursing staff in this case as they were clearly acting out of concern for the safety of a newborn baby . '' The late Robert F. Kennedy 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 . CNN 's Yon Pomrenze reported from Mount Kisco and Greg Botelho from Atlanta .
NEW : A nurse testifies that Douglas Kennedy twisted her ankle and kicked another nurse . NEW : The defense questions the nurse 's motives and calls her ` ` abrasive , confrontational '' NEW : Judge will hear case against Kennedy , who is charged with assault and reckless endangerment . He is the son of the late President Robert F. Kennedy .