The U.S. teenager facing 15 years in jail for the murder of her mother grinned nervously as she took her baby to court in Bali again today - while maintaining her innocence. Heather Mack,19, smiled and laughed as she cradled her baby Stella - born last month - in a holding cell at the Denpasar District Court as she announced: 'I should not be sent to prison because I'm innocent. 'I haven't murdered anybody. I didn't murder my mother.' She was also filmed singing the Rihanna hit Umbrella as she nursed the infant outside of the courtroom. Heather Mack, pictured smiling behind bars, is accused of the murder of her socialite mother, Sheila von Wiese-Mack . The new mother took baby Stella to court with her, who was born last month at a prison hospital . Prosecutors have asked judges in the holiday resort to jail Mack, left with baby Stella, for 15 years and Schaefer, right, for 18 years . Mack has said that she intends to keep Stella with her until the child is two years old . The teenager has previously said that her smile is a 'disguise,' according to the Chicago Tribune. 'If I allow myself to grieve whatsoever I'm in a complete state of depression,' she told the Tribune. 'The smile is actually a disguise I wear to survive here.' Innocent: Baby Stella was born in hospital last month . Both Miss Mack and her boyfriend now face an anxious five days after court officials indicated that the judges would declare their verdict next Tuesday. Chief Prosecutor Eddy Wijaya insisted  that pleas for lighter sentences for the pair, because of their young age and new-born daughter, should be ignored. He argued that the physical evidence in the hotel room and texts between the defendants revealed their dislike of the 62-year-old victim pointed to premeditated murder. Both Mack and Schaefer openly displayed nervousness as they waited to go into court today, aware that the case against them was drawing to a close and the judges were close to announcing sentences. The young mother bit her nails in the holding cell and smiled nervously as cradled her baby and Schaefer chain-smoked as he paced up and down his own cell. At an earlier hearing the prosecution team argued that the murder of her mother, Sheila von Wiese-Mack had been premeditated and insisted Mack and Schaefer, should go to prison for 15 and 18 years respectively.. Mack had denied the premeditated murder of the Chicago socialite in the five-star St Regis Hotel, Bali, in August last year. But judges on the holiday island, under Indonesia's legal system, said they accepted the Prosecution's argument of guilt before the defence team had offered their reasons for leniency. Schaefer has admitted unintentionally killing Mrs Mack, telling the court  that he had lashed out while defending himself after Mack's mother grabbed him by the throat in an argument in her hotel room. The panel of three judges accepted the prosecution's argument that Mr Schaefer had intended to murder Mrs Mack when he went to her hotel room because she had racially insulted him and objected to his relationship with her daughter. Her body was found crammed into a suitcase which had been loaded into a taxi with the couple's other luggage at the hotel after they had run out through the beachside exit of the premises. New father: Tommy Schaefer looks dotingly at his young daughter as he is led away from court in handcuffs . Mack drapes her arms across the bars of the holding cell as she waits to be taken into court . Mack, looking bored in her cell, now faces a five day wait to find out her fate . Baby Stella was born by cesarean section last month after Mack was transferred from her prison cell to hospital. Lawyers for both defendants have asked the judges to reject the demands for long prison sentences, insisting the murder was not premeditated but that Mrs Mack was killed amid moments of panic and distress. When asked by reporters about a possible 15 year sentence, Mack replied: 'It's not the verdict today is it?' When pressed about it, she added: 'Less than that (15 years), I'm innocent.' The couple are accused of killing socialite Sheila von Wiese-Mack, 62, in the five-star St Regis Hotel, Bali, in August last year . After today's hearing the couple were taken back to Kerobokan prison, which, if the judges agree to the prosecutions demands could become their home for the next 15 and 18 years. Mack has already told officials that she intends to keep baby Stella with her in prison for the maximum two years that youngsters are allowed to remain with their mothers. But it is understood that Schaefer's mother, Kia Walker, has been pressuring her to allow the baby, which had to be treated for jaundice within days of her birth, to be taken back to the US.
Heather Mack,19, tells Bali court she did not kill Sheila von Wiese-Mack .
On trial for mother's murder with 21-year-old boyfriend Tommy Schaefer .
Mack gave birth to baby Stella Schaefer last month in prison hospital .
Couple facing a nervous five day wait for judge's to return their verdict .