The California mother who was charged with manslaughter last week in the death of her newborn son on Friday was arraigned on an upgraded murder charge. Samantha Green, 23, pleaded not guilty to the new count after Judge David Rosenberg rejected the defense's claim that the woman was the target of ‘vindictive prosecution.’ Prosecutors appealed to the judge to change Green's charge from manslaughter to murder after claiming to have uncovered new evidence in the death of her 20-day-old son, Justice Rees, over the past week. Overcome with emotion: Samantha Green, 23, is seen being comforted by her public defender Traice Olson Friday after pleading not guilty to an upgraded charge of murder in the death of her newborn son . Higher stakes: Prosecutors appealed to the judge to change Green's charge from manslaughter to murder after claiming to have uncovered new evidence . Police found the body of 20-day-old Justice Rees (right) in swampy land near the Sacramento River last month after he and Green (left) were reported missing . In response, Green's public defender, Tracie Olson, demanded to be presented with the new information and accused the opposing side of moving the goalpost after her client had agreed to plead guilty to the lesser charge of manslaughter, reported Sacramento Bee. Dressed in a striped green-and-white jumpsuit, Green appeared dejected and wept in court. Supervising Deputy District Attorney Rob Gorman declined to go into detail about the new evidence but defended the timing of the request to amend the complaint against Green. Gorman acknowledged that that while it may look ‘suspicious,’ the information they have obtained since Green’s arraignment March 4 warranted the charge upgrade. ‘We now believe that Ms. Green can be legitimately charged for murder,’ said Gorman. Green, of Woodland, made her first court appearance last Wednesday following her weekend arrest in the death of her baby son. The original charges against Green also included an enhancement for inflicting great bodily injury on a child under age five during the commission of a felony. The boy's body was found with no obvious signs of trauma last week in a swampy area. Sheriff's investigators said he may have died from drowning or hypothermia near the rural town of Knights Landing, about 30 miles west of Sacramento. Green, who had been reported missing with her son two and a half weeks ago, was found a day earlier looking disheveled and bruised. Last week, Green (pictured in court March 4) pleaded not guilty to an involuntary manslaughter charge in her baby's death . She told authorities that she and the boy had been abducted, but police have said they do not believe her story. Despite the charges, Green's family said they are standing by her. 'Our family is grieving not only for the loss of our grandson Justice, but also the possible loss of our daughter Sami Green,' Green's parents, Randy and Laurie, said in a statement released on Sunday morning and shared by CBS. 'She has never been in trouble with the law. We know in our heart that Sami would never do anything to intentionally harm her newborn son Justice. She loved him very much. 'Her entire family supports her through this most unbelievable time in our lives.' Justice had methamphetamine in his system at birth, reported KCRA, but Green and the boy's father were allowed to take him home after passing a drug test and agreeing to a safety plan put forward by Child Protective Services. Samantha Green was reported missing February 24 after she failed to visit her father, Randy, three days earlier, as planned. Her partner Frank Rees posted on Facebook a day later begging Green to come home with their son. 'If anyone sees my beautiful fiancé [sic] please tell her that EVERYONE is worried sick about her and Justice,' he wrote. 'We love you Samantha. Just come home babe. I miss you and our son sooooo much. Whatever it is you want different we can fix. I love you momma.' Her partner Frank Rees (right), who is also Justice's father, is supporting Green (left; right with Rees) Crews looked through the Ridge Cut Slough for hours before finding Justice's body, which Green said was in the water . Later that day, she called police to say she had been abducted with her son and that the boy was missing. Passerby Ricardo Villaseñor then came upon Green, wet and shouting for help near the Ridge Cut slough, News 10 reported. Villaseñor said although Green seemed disoriented, she explained to him she and the baby had been abducted in town, but that she had no idea how she'd wound up next to the river. 'She was badly bruised,' he said. 'She had no shoes. She was kind of left for dead, it seemed like.' She told him she knew her baby had frozen to death, and though she said she didn't know exactly where he was, she said he was somewhere in the slough. Green was admitted to Woodland Hospital and was later released. She was then arrested and charged with murder. After her arrest, Yolo County Sheriff Ed Prieto said: 'We have come to the conclusion that Mrs. Green was the sole individual responsible for the death of her child.'
Samantha Green, 23, pleaded not guilty to upgraded murder charge . Last week, she was arraigned on a count of involuntary manslaughter in the death of her son, Justice Rees . Prosecutors asked a judge to amend the complaint against Green after claiming they had uncovered new evidence . Green's public defender accused prosecutors of moving the goalpost after learning that her client was going to change her plea to guilty . Justice's body was found with no  signs of trauma in a swamp in late February .