DENPASAR (Reuters) - A US man and his pregnant girlfriend presented their defence on Wednesday at a hearing where they stand accused of murdering the woman's mother, whose battered body was found stuffed in a suitcase on the resort island of Bali last August.

Tommy Schaefer and Heather Mack, both from Chicago, argued through their lawyers that the prosecutor's case lacked credible witnesses and was unclear on where the crime took place. "We object to the prosecutor's letter because it's not valid," said Edi Iswahyudi, a member of Schaefer's legal team.

Schaefer was charged last week with premeditated murder and Mack is charged with assisting her boyfriend in the killing of her mother, Sheila von Weise-Mack.

Under Indonesian law, the defendant does not enter a plea until the end of the trial.

According to Schaefer and Mack's defence statements, which were read out in Denpasar District Court, evidence in the case was also prone to manipulation.

The presiding panel of three judges will decide on Jan. 28 whether the trial will proceed or if the case will be dismissed due to inadequate evidence.

Schaefer and Mack, both of whom were brought handcuffed to the court, could face the death penalty if found guilty.

A US court ruled on Tuesday that Mack can have access to US$150,000 (S$187,545) of her trust fund to pay legal bills and food costs. Bali police conducted a four-month investigation into the killing that included a re-enactment with the defendants at the luxury hotel where Wiese-Mack's body was found.

Other evidence submitted to prosecutors included CCTV footage showing the couple speaking to a taxi driver after dropping the bloodied suitcase along with other luggage outside the hotel.