Following the Battle of Hoth and the destruction of their primary headquarters in 3 ABY, the Rebel Alliance was weakened and forced to scatter around the galaxy to avoid the Galactic Empire's forces. To allow Rebel divisions to locate each other for an eventual regrouping, they utilized encrypted messages; these were, however decrypted by the Empire which proved the need for an entirely new and original encryption system. Protocol droid C-3PO suggested the ancient language Trawak as a viable means of communication, since the Trawaki were long extinct and no speakers of the language existed anywhere in the galaxy. The only source C-3PO believed could speak the language and thus act as a key to a new cryptographic system was the Autonomous Translator Module, Mark II, an ancient talky droid kept in the Galactic Museum on Coruscant. Following a successful heist performed by the Pathfinders, the talky was retrieved and forced to create the cryptographic system for the Rebels.
This tactic proved to be effective; however, to power it required the cyborg Lobot to utilize his AJ^6 cyborg construct to interface with the droid which severely weakened him. Realizing that the talky hurt his friend, Lando Calrissian attempted to intervene and disconnect it, but was prevented by Leia Organa and Kes Dameron, as the droid was in the process of actively transmitting emergency broadcasts to other rebel groups. Despite Calrissian's outburst, C-3PO revealed that he had managed to learn Trawak himself by observing the talky, making the droid useless and allowing the rebels to disconnect it and save Lobot. It was then safely locked away in Home One as the sole key to the Alliance's encryption codes other than C-3PO, and kept under guard as a vital rebel asset.
Despite Lobot ultimately surviving the ordeal, Calrissian came to believe that the Alliance cared very little about his friend or himself. Having come to that conclusion, Calrissian stole the talky from its storage by incapacitating the rebel trooper guarding it and sold it to Jabba Desilijic Tiure to repay the sizable debt he owed to him, no longer caring about the risk to the Alliance should the gangster use it to learn their codes. During a mission to rescue Han Solo during an auction in Jekara, Calrissian took the droid on board the Millennium Falcon, activated its transponder beacon and pushed it out of the airlock for Jabba to retrieve. However, the droid briefly showed it would be able to free Lobot from his implants, only for the Falcon to leave before Calrissian could retrieve it.
Overtime, Calrissian became more attached to and invested in the Alliance, becoming a rebel believer himself and someone who was beloved amongst its ranks. However, after the emergence of the Scourge, an artificial intelligence created from the merge of the Spark Eternal and an ancient intelligent droid and capable of infecting droids with its personality, Lando was again forced to retrieve the talky as Lobot had been kidnapped and experimented upon by the intelligence. Following the battle on Epikonia and the Scourge's defeat, Calrissian retrieved his friend and took the talky out of storage in the Falcon, forcing it in gunpoint to restore his friend's help. With no leverage against Calrissian or other options to protect itself, the talky agreed to repair Lobot in exchange for Calrissian confessing to his betrayal of the Alliance. Lando indeed confessed to having stolen the talky fully aware of the repercussions it could have on the Alliance, and the Module repaired Lobot. As soon as the Falcon returned to the fleet, Lando was arrested and placed in a detention cell.
Lando Calrissian was charged with treason, mutiny, desertion and insubordination and set to be tried according to the Corellian code of military justice. The code classified the crimes he was charged with as capital offenses and stipulated the death penalty if he was found guilty. Despite General Crix Madine and Admiral Gial Ackbar initially arguing that Calrissian should be immediately executed, Mon Mothma and Leia Organa advised against it for both morale and political reasons; Calrissian was well-liked among the rebels and his execution would be seen unfavorably after the inevitable investigations that would follow the conclusion of the Galactic Civil War. Ultimately, the Alliance High Command decided to move forward with a trial to reveal the full extent of Calrissian's crimes and offer him the chance to defend himself.
The trial was held in Home One and presided upon by Mothma, Madine, and Ackbar as acting Magistrates. Mothma attended the trial via hologram as she was in a diplomatic mission to Uveron at the time. The Rebel Alliance was represented by its chief legal representative Captain Darrien Muskray, while Calrissian's defense team was comprised of lawyer Salli Georgio and paralegal Three-Ell.
The trial began with Muskray's opening arguments and witness examination, which was briefly interrupted by Georgio initially requesting her droid be allowed access to the ship's audio recording system to keep notes of the proceedings and then feigning ignorance of the Corellian code and requesting a recess to be able to study it. Her request for a recess was, however, denied by the Magistrates on the basis that Georgio as a lawyer should be aware of one of the major law systems on the galaxy. Muskray then continued his arguments by calling the Autonomous Module on the stand and provided its bit-codes to the court to prove that its memory banks had not been altered or modified during the last century and verify its testimony as true and accurate. Following that, Muskray questioned the talky first on its importance for the Alliance's secure communications system and then asked it to testify on its kidnapping by Calrissian. Georgio then cross-examined the talky, asking it whether it was possible it was acting under the influence of the Force, which was rejected as impossible by Luke Skywalker who was present on the trial. Muskray then continued the examination and presented a recording of Calrissian taken by the Module, which showed the General confessing to his actions on board the Falcon.
During Muskray's arguments, a group of Scarabi mercenaries infiltrated the compound where Mon Mothma resided on Uveron and kidnapped her after killing her guards. The trial was immediately interrupted and Ackbar scrambled the fleet as per , leaving Home One alone. Georgio used the opportunity to cite Section 811, sub-section nine, point four of the Corellian code which stated that in the case of a tribunal magistrate being incapacitated causing the proceedings to conclude without them a mistrial should be declared. The argument was, however, rejected by the magistrates as the trial had not concluded and Mothma was theoretically able to rejoin at a later date.
Muskray continued with his arguments calling Leia Organa as a witness to testify on Calrissian's previous record. Organa revealed the betrayal at Bespin during which Calrissian sold the rebels to Darth Vader in exchange for Cloud City's independence, which resulted in Han Solo's capture by Boba Fett. Organa concluded her testimony by expressing her opinion that despite Calrissian eventually helping the team escape Cloud City did not mean he had actually changed his selfish ways. Following Muskray, Geogio in turn cross-examined Organa and presented her with Calrissian's bank account balance during the Imperial occupation of Bespin, asking her why she believed Calrissian did not use his considerable wealth to escape Cloud City as soon as they arrived. Organa answered that Calrissian could not leave his people behind, which concluded Geogio's examination.
Based on information provided by Calrissian (through Chewbacca, since Calrissian knew that the Rebels would not trust him), Calrissian, Chewbacca, and a Pathfinder team led by Kes Dameron searched numerous Scarabi safe houses, eventually finding her at Safe House 4. After Calrissian freed Mothma, she rejoined the magistrate and the trial was resumed.
Salli Georgio, advocate for the defendant, took the stand following the resumption of the trial and called two witnesses to testify in Calrissian's defense. The first witness was Lobot, who was questioned by Salli on the circumstances of his survival from his implants' takeover as well as Lando's character. Lobot described the lengths Lando had gone to in order to cure him and the loyalty his friend had to the Alliance. When questioned on how a loyal Rebel soldier betrayed what he supposedly believed in, Lobot explained that he was simply more important to Lando as a friend than the Alliance as a cause; however, being cured, Lando would have nothing more important in his life than to fight for them.
The second witness was Calrissian himself, who, before taking the stand requested a sidebar with Leia Organa. Despite the request being rejected on the basis of the Corellian code's provisions, Lando spoke before the room and offered Leia a full breakdown of Jabba's Palace's layout and the location of Han Solo's carbonite block in exchange for Lobot being allowed to leave the Alliance without repercussions. Lando then took the stand and stated he regretted accepting the trial as a fair punishment for his actions, as all Rebels in service of the Alliance had broken the law on the basis of their own personal moral code, and sentencing him would be hypocritical.
Following Calrissian's testimony, the advocates again took the floor to summarize their case, beginning with Captain Muskray. Salli Georgio however interrupted his argument, accusing the Magistrates of running a mock trial with a predetermined result, and expressing her belief that if the Alliance wanted to win the war they would have to live with Lando's betrayal and use his connections to their advantage.
After five minutes of deliberations, the Magistrates returned to the room and announced their decision. Lando Calrissian was found guilty of treason against the Rebel Alliance, insubordination and other infractions of the Corellian Code of Military Justice and sentenced to a fine of two hundred and fifty million credits, suspended pending the end of the Galactic Civil War and liable to being reduced if Lando's future actions proved merit to such a reduction.