The British teenager allegedly gang-raped in Cyprus could face a three-year wait to exhaust the legal process relating to her conviction for lying. The long delay increases pressure on the Foreign Office to lobby Cyprus to expedite the appeal process.

The student, who cannot be named for legal reasons, was ruled to have “wilfully indulged in public mischief” by claiming that she was raped by a group of male Israeli tourists while on holiday in Ayia Napa last July.

The verdict led to widespread criticism of both the Cypriot justice system and the judge who heard the case, Michalis Papathanasiou. The 19-year-old, who has been on bail since the end of August after spending a month in prison, could face up to a year in jail and a £1,500 fine when her sentence is handed down on Tuesday.

There have been calls for the teenager, who planned to go to university, to be pardoned but her British lawyer said this would be insufficient as the original conviction would still have an impact on her future. “Her Cypriot lawyers explained to me that if you are pardoned it would still count as you being convicted,” said Michael Polak of the campaigning group Justice Abroad. “The injustice for her is of being convicted for the offence. There’s also the consideration of the effect it could have on the professions she could be a part of, the associations she could be a part of, the places she could travel to. So she will definitely be appealing [against] the conviction.”

A presidential pardon would be possible only if the student is given a jail sentence on Tuesday. “A pardon can only be given if he convicts her without suspension to a period of more than a month in prison,” said Nicoletta Charalambidou, who heads the Briton’s four-strong legal team.

Her legal team has 10 days to put in its appeal after the sentence is handed down. But the appeal process is normally long. Charalambidou told the Observer: “We will seek an expedition procedure which would allow the case to be heard within six months.” If the appeal is unsuccessful, lawyers will resort to the European Court of Human Rights, raising the prospect of the case lasting at least three years. Polak said he hoped the request to expedite the case would be well received after the foreign secretary, Dominic Raab, raised concerns. “The foreign secretary has been involved so hopefully we can call on the Cypriot authorities to facilitate that [expediting the case]. It’s in everyone’s interest, including [that of] Cyprus, to get the matter dealt with as quickly as possible.”

Papathanasiou’s behaviour during the trial has been described as “vindictive” but Polak, who confirmed the teenager’s legal team was considering making a complaint to the relevant legal authorities about his behaviour, said the teenager had been buoyed by messages of support. “Her GoFundMe page has received a lot of support from Israel, the United Kingdom and all around the world. There are lots of messages that people have been sending to me to pass on to her, wishing her the best of luck, which is heartwarming for her. It’s important for her to know at this difficult time that people are supporting her and the positive coverage in the press is also important for her.”

The case has seen the Cypriot legal system subjected to intense scrutiny. Law experts have expressed concern about the way potential evidence, including that provided by the state-appointed pathologist who examined the teenager, was collected.

“An expert witness examined pictures [of the teenager] and what she said [had happened] and observed blood and bruising in her vagina that accorded with what she was saying,” Polak said. “Since this case, we’ve had other people getting in touch to report serious sexual offences, similar problems in Cyprus, and other cases where foreigners have felt that they haven’t had a fair hearing in the courts, from property disputes to all different kinds of matters.”

The teenager’s lawyers claim her retraction of the rape claim 10 days after it was alleged to have taken place was made under duress and without legal representation, something that could become an issue for the European Court of Justice. They say she was held for eight hours, subjected to quick-fire questioning and aggressive behaviour, denied access to a lawyer and told that if she did not agree to retract her statement she would next see her mother when she appeared in court in handcuffs.