The trial of British citizen Laura Plummer has been postponed to Boxing Day after confusion in the courtroom caused her to unintentionally plead guilty to charges of drug trafficking.

Plummer is accused of trafficking after bringing 290 tablets of the opioid painkiller Tramadol into Egypt. She and her family have maintained that she did not bring the tablets into Egypt for resale, but rather to give to her partner to help his back pain.

Tramadol is a controlled substance in Egypt, where trafficking the drug can lead to up to 25 years in prison or even the death penalty in rare cases.

Mohamed Osman, Plummer’s lawyer, told the Guardian that translation issues in the Red Sea criminal court in the Egyptian town of Hurghada caused the postponement of the trial, after Plummer’s statements were wrongly translated to the judge.

“We had a big problem today,” he said. “We had a translator for Laura, which the judge didn’t use, and instead called on a member of the bench to translate for Laura.” Osman branded this development “strange”.

He continued: “The main judge demanded that a member of the bench ask Laura whether she traded or dealt in narcotics. The member of the bench then asked her in a different manner, saying: “You are accused of dealing drugs,” to which she answered ‘yes, I am accused of this’. This was was translated to the main judge as Laura admitting that she did the crime.”

Osman argued that this mistranslation made it look as though Plummer had pleaded guilty to drug trafficking, “but she didn’t,” he said.

Both Plummer’s family and her lawyer described Plummer’s distress, saying that she was crying openly in the courtroom and sleep deprived. Osman denied reports that Plummer appeared in court in handcuffs. Plummer’s mother, Roberta Sinclair and Plummer’s partner Omar were reportedly present outside the courthouse.

Plummer was arrested on arrival at Hurghada airport on 9 October after a scan of her bags revealed she was carrying a large supply of Tramadol. She was later forced to sign a 38-page confession document in Arabic, which she does not read or understand. Her family have since issued an apology to Egypt, saying “we trust Laura is in good hands and will be treated fairly”.

Osman said that he objected openly in court on Monday to the way that Plummer’s statement was handled. The trial was then postponed to Tuesday, in order to allow the defence time to provide more evidence. “I sat with Laura and informed her that she has to protest against [the mistranslation] tomorrow, and to make this clear in the minutes of the trial session. She has demanded the presence of an official translator or to get permission to use the translator she already has,” he said.

“It is very dangerous to have a judge that has difficulty speaking English with an English citizen, when it comes to a crime that could lead to the death penalty,” he added.

Additional reporting by Adham Youssef