Davros's trial (Revelation of the Daleks)

During a schism following the Dalek-Movellan War, Davros was captured by the Daleks and placed on trial on their home planet, Skaro. Although accounts differed on the exact circumstances, all concurred that Davros was eventually able to turn the tables on the Dalek Empire as a consequence of his trial, rising to the rank of Dalek Emperor himself.

The Time Lords understood Davros's trial, as well as 's trial by the Daleks, to have been conducted for strategic reasons rather than to offer any genuine possibility of clemency. (PROSE: Dalek Combat Training Manual)

Capture
Having been alerted by Takis, a worker at Tranquil Repose on the planet Necros, Daleks loyal to the Supreme Dalek came to Tranquil Repose where they captured Davros. Informing him that he was to stand trial "for crimes against the Daleks", the Daleks took Davros with them. (TV: Revelation of the Daleks)

En route to Skaro, the ship carrying Davros crashed on the planet Lethe. Davros was rescued. He set himself up as "Professor Vaso", altering the perceptions of the humans on the colony so they would not recognise him as the "Great Healer". He attempted to create a new machine, a Juggernaut based on a Mechanoid design.

Lethe's atmosphere prevented the Supreme Dalek retrieving Davros directly, but its forces intercepted the Sixth Doctor's TARDIS, forcing him to serve as an agent of the Daleks and stop Davros's researches and manipulations. The Doctor discovered two of Davros's Necros Daleks had survived the crash, but were destroyed following Davros's final gambit on the colony and the Supreme Dalek's intervention. (AUDIO: The Juggernauts) Nevertheless, the Time Lords noted it was possible other Necros Daleks survived and were present on Skaro during the trial, writing that they could have helped Davros establish his rule. (PROSE: Dalek Combat Training Manual)

Account 1: Execution of Davros
According to one account, Davros was returned to Skaro where he was strictly watched at all times. Eventually, he was brought before the Dalek Supreme Council and the Black Dalek for trial. As Davros had expected, the trial was mostly a farce played out before the Daleks who watched the events on film. He was allowed to speak in his defense, the Black Dalek knowing that their crazed creator would not be able to resist the opportunity. Davros launched into an impassioned plea to the Daleks to swear allegiance to him, and to allow him to lead them to greater victories once again. He promised to redesign their casings so as to make them stronger, swifter and more enduring, and to oversee their destiny as supreme beings in the universe.

Ultimately, Davros was cut off by the Black Dalek, who spoke in its turn. Davros had never renounced his claim to be the supreme ruler of the Daleks; to him, they were nothing more than an extension of his own purposes. The Black Dalek insisted, however, that the Daleks could do what was needed without Davros, who would undoubtedly seize his first opportunity to reprogram them to obey him again. As Davros could not be trusted, it was deemed necessary for him to be exterminated so that the Dalek race could achieve its own destiny. Davros denounced the Daleks as fools if they were to reject him, promising that without him they were doomed. The Daleks refused to listen further, and sentenced their creator to death. Davros managed one last attempt to regain power, for there were some within the Dalek ranks, including even within the Supreme Council, who felt that he was possibly telling the truth. At any rate, there were some Daleks who felt that Davros could be used and then discarded once his mind had been drained and utilized. A rescue attempt was staged but was anticipated by the Black Dalek had been anticipating this; since the disastrous losses of the Movellan War, he had known that there was talk of overthrowing the Council and reforming the Dalek power scheme. The true and only reason Davros had been brought to Skaro was to force the rebel elements into the open. The Black Dalek and his forces struck against whom they deemed to be traitors. They succeeded in slaying the dissidents, leaving Davros with no means of escape. The Black Dalek ensured that the Dalek creator was condemned, and he was placed within a matter transmitter. It was set on a broad beam, and his component molecules were scattered about Skaro's sun. Despite his rantings and boasts, this resulted in the apparent death of Davros and the end of the war for the final control of the Daleks.

In the aftermath, the Daleks, still lacking the army they desired, executed an elaborate plan to conquer the galaxy involving the construction of a Time Destructor and the formation of an Intergalactic Council. This plot was thwarted by the First Doctor, and so the Dalek Wars lingered for the next couple of centuries as the Daleks were gradually pushed back to Skaro. There, the Dalek Prime launched a new plot to use the Second Doctor isolate the Dalek Factor so it could be spread throughout human history. This backfired when the Doctor implanted the Human Factor into what became the Humanised Daleks, resulting in the Dalek Civil War which resulted in the Final End of the Dalek Prime and the Dalek species itself as Davros had warned. (PROSE: The History of the Daleks)

Other accounts, however, indicated that the Daleks had survived the Human Factor incident, (COMIC: Bringer of Darkness) and that the return of Davros was still within their future. (PROSE: Dalek Combat Training Manual) Incidentally, the circumstances of this account of Davros's trial after Necros, including its true purposes and the apparent execution of the Dalek creator, bore similarities to an account of a later trial of Davros following a staged destruction of Skaro. One witness to this event was the Eighth Doctor (PROSE: War of the Daleks) who would be embroiled in the Last Great Time War along with Davros, who followed the Dalek Emperor. (PROSE: Father of the Daleks, TV: The Night of the Doctor, PROSE: The Third Wise Man)

Account 2: Before the Golden Emperor
According to one account, Davros was then taken to Skaro, where he was put on trial by the Golden Emperor. He tried to argue that under the Emperor, the Daleks, lacking his guidance, had seen their destiny curtailed, and that only he could allow them to advance once again. Although some Scientist Daleks were privately swayed by the argument, the irate Emperor thundered that it was in command of the Daleks' destiny, not Davros, and ordered his extermination.

Before the sentence could be executed, however, the Sixth Doctor released a computer virus onto the Daleks and saved Davros, taking him on board his TARDIS and telling him of the Hand of Omega, as part of a scheme that would pay off later in both the Daleks' and the Doctor's histories, (COMIC: Emperor of the Daleks!) in the form of the Shoreditch Incident. (TV: Remembrance of the Daleks)

By suggestion of the Doctor, (COMIC: Up Above the Gods) Davros hid himself on Spiridon, along with his empire of Daleks. The Daleks who had put him on trial before came to return him to Skaro, but his Daleks held them off. Davros detonated the planet, killing the Daleks. He woke highly injured, four days into the Imperial-Renegade Dalek Civil War, in a new casing as the Dalek Emperor. (COMIC: Emperor of the Daleks!)

Account 3: Like "second hand goods"
According to a second account, the trial was not a legal endeavor but instead the Daleks "trying out" Davros to solve the schism that had appeared in their empire (AUDIO: Innocence) after the Dalek-Movellan War. (PROSE: Remembrance of the Daleks) As Davros put it, the Daleks were "trying [him] out" as if he were "second hand goods" that needed to be tested before being used. Despite finding the Daleks' request for direction pathetic, he agreed to help and began to reflect on the past. (AUDIO: Innocence)

Account 4: The interference of the Thal
According to another account, Davros encountered the Thal Lareen while en route to Skaro. Lareen was using a stealth suit that made her invisible to Dalek scanners. Lareen attempted to find Davros's "good side," and believed she had succeeded. She gave Davros a capsule containing an enhanced version of the Movellan virus and asked him to release it during his trial. This would destroy all Daleks on Skaro, and make Davros a hero.

Upon arriving on Skaro, Davros found that the Supreme Dalek had a new casing created. With the Golden Emperor apparently absent, the Supreme Dalek planned to be moved to the new casing and named Emperor of the Daleks after Davros's execution. During his trial, Davros told the Daleks of the Movellan virus, and proved his loyalty to the Dalek cause by refusing to release it. He then told them that Lareen was on Skaro and ordered them to exterminate her. The Daleks were impressed with this show of loyalty, and named Davros Emperor of the Daleks. (AUDIO: The Davros Mission)

Behind the scenes
The Discontinuity Guide states that, having been tried by the Supreme Dalek, Davros won the argument regarding human tissue and mentality and took over the white/gold Daleks, augmenting them and himself. He became Emperor, potentially having been influenced by the Fourth Doctor's reference to a Dalek Emperor in the midst of his interrogation during his incursion into Dalek history. However, some Daleks rebelled over the issue of racial purity.

The Dalek Handbook claims that there were no "non-Skaroene" witnesses to Davros' trial.

AHistory speculatively dates Davros's trial in Emperor of the Daleks to c. 4625, a decade following the Necros Incident.