Broadcast live on television since it started on February 12, the trial in Madrid over a failed bid to prise Catalonia from Spain in October 2017 is scheduled to end on Wednesday with a sentence expected in the autumn.
One of 12 separatists in the dock, Junqueras faces up to 25 years in prison for rebellion and misuse of public funds, the heaviest sentence.
Behind bars since November 2017 after choosing to remain in Spain rather than escape following Catalonia's failed declaration of independence, the trial propelled the lifelong supporter of secession back into the spotlight.
In his last comments to Spain's Supreme Court on Wednesday, Junqueras remained defiant.
"Voting... and defending the republic from a parliament can not be a crime," he said.
In February he told the court, "if at any time I put a bit of passion into my explanations... it's because they've not been letting me speak for a year and a half," before launching into a passionate defence for 90 minutes.
Another way of expressing himself was standing in a general election on April 28 and being voted in to Spain's lower house, along with three other defendants who are also in jail. They were all subsequently suspended from parliament.
But that wasn't the end. On May 26, Junqueras was elected to the European Parliament and hopes to keep that post, though how that will happen remains to be seen.
"I presented myself as a candidate most of all because it is a way to condemn the repression and democratic regression of the Spanish state," Junqueras told AFP in a written interview from prison.
He presents himself as a "political prisoner," a claim fiercely denied by Spain's judiciary and government, which insist he is being tried not for his opinions, but for breaking the law.
Born on April 11, 1969 in Barcelona, Junqueras was educated at an Italian religious school.
He is a devout Catholic who speaks Spanish, Catalan, English and Italian, and once did research at the Vatican where he met the man who would later become pope Benedict XVI, close friend and adviser Raul Murcia told AFP in February.
A history professor at the Autonomous University of Barcelona, he was elected a European lawmaker in 2009 and picked to head the pro-independence, left-wing ERC party in 2011.
The affable Junqueras, described as a "teddy bear" by Catalan socialist leader Miquel Iceta, became vice-president of Catalonia in January 2016.
He was later tasked with organising a highly sensitive secession referendum on October 1, 2017, despite a court ban on holding such a vote.
Junqueras commands loyalty but remains inscrutable to many, with a reputation for sidestepping questions.
"Despite days and days of conversations with him, I still question who Oriol Junqueras really is and what his personal and political project is for Catalonia," Santi Vila, one of his former government colleagues also on trial, wrote in his book.
Regardless, Junqueras was seen as the more pragmatic voice to the staunch idealism of Catalonia's former president Carles Puigdemont, who has since fled Spain.
Enric Millo, who was Madrid's representative in Catalonia before and during the 2017 crisis and had frequent dealings with Junqueras, said he had initially hoped to negotiate a solution.
"He talks really well, almost like a priest... and all of a sudden when it comes to act he draws the knife," Milo said, calling Junqueras "two-faced".
The independence referendum took place, marred by police violence.
After that, all eyes were on whether Puigdemont would declare independence or instead call snap regional polls -- a conciliatory move.
But it is widely believed that by then, neither Junqueras nor Puigdemont wanted to be labelled "traitors" to the independence movement by calling elections.
So it was that on October 27, the majority-separatist Catalan parliament declared independence from the rest of Spain and Madrid promptly ousted the regional executive.
Several days later, Puigdemont and several others fled to Belgium.
Junqueras chose to remain "because of his responsibility towards fellow citizens and also a little for his family," said Murcia.