"The convict claims he committed the incriminated acts involuntarily and was provoked by the United Kingdom's secret service agents," the chairman of the judicial college said presenting the appeal.
During his previous trial, Campbell said that Robert Jardine, allegedly British secret agent and witness to the case, talked him into engaging in weapon smuggling.
The Court of Appeal asked the Irishman about their relations, and he said they met through cigarettes smuggling business. "We got acquainted through cigarettes business," Campbell said. Asked by the judge whether the business was legal, he said: "Contrabanda."
Ingrida Botyrienė, defending, asked the court to demand additional information about Jardine's activities from the United Kingdom.
"There's no document in this case that would define the limits of power of this person," she said.
Gedgaudas Norkūnas, prosecuting, said they received confirmation from the UK Home Office that Jardine's activities were legitimate and that it was enough.
The Court of Appeal is expected to give its ruling in two weeks.
The prosecutor had asked the court to increase the sentence to 16 years.
Campbell said in his appeal that Vilnius District Court had failed to properly evaluate the fact that he had been provoked and was insufficiently critical about testimonies of secret service agents.
"The crimes Vilnius District Court had found me guilty of and sentenced me for were "made up" by the UK secret service MI5 and realized together with the State Security Department of the Republic of Lithuania," the Irishman's appeal says.
Campbell was arrested in Vilnius in January, 2008, after he purchased weapons from a secret agent pretending to be a gun seller. He was sentenced to 12 years in prison as, according to the court, his actions were controlled by security officers and prevented real damage.
At a court hearing in August, the prosecutor cited secret witnesses as saying that Campbell had asked what amount of explosives was needed to blow up a government vehicle and said he planned to use the weapons against people.
The Real IRA is a paramilitary organization, which aims for a united Ireland, that is, including Norther Ireland that is now part of the UK. Under Irish laws, Real IRA is an illegal organization and the Council of Europe has listed it as being related to terrorist attacks.