The seven men and one woman are accused of blocking trucks carrying cattle to auction from Frontenac Institution during protests in August 2010.
They have each pleaded not guilty to a charge of mischief over $5,000.
The accused argue they were forced to organize protests and try to stop cattle trucks after the government decided to close the farms several months before a vote on a public safety committee motion.
"The government knew Parliament was going to vote," co-accused Andrew McCann, a 35-year-old baker, said outside court.
"They nonetheless went forward and did the thing that they knew was the death knell for the farm by getting rid of the herd."
Police arrested 24 people over two days of demonstrations, but many accepted a deal to donate to charity through a diversion program.
The accused on trial refused a deal from the Crown.
They called three witnesses over the two-day trial: former Frontenac Pen Farm supervisor Ronald Amey, Save our Prison Farms campaign co-ordinator Dianne Dowling, and former Liberal MP Mark Holland.
Crown attorney John Skoropada objected to the relevance of the witnesses, adding they gave a "significant" amount of hearsay.
Judge Rommel Masse allowed them to testify, but reserved the right to strike the evidence at a later date.
Court has heard the accused were warned they would be arrested if they crossed cement barricades to block the cattle trucks leaving the institution.
Police video showed they were unable to reach the entrance before police arrested them from within the crowd.
"If they were going to take the cattle away, it was going to be the certain end of the farm," Dowling testified.
"The options the government made left us with no choice."
Holland, who authored the motion that was voted on in Parliament, testified he didn't know much about prison farms at first.
Once he got involved as the Liberal public safety critic, he said he grew to understand their importance.
He said the government wouldn't provide detailed reasons for closing the farms, other than they cost too much.
"Getting information from the government was impossible," Holland said. "I felt very strongly this was a good program."
He said the farms changed the lives of inmates.
Supporters of the program said a strong work ethic and sense of responsibility were among the skills developed through the initiative.
In closing submissions, Skoropada asked Masse to strike evidence from the witnesses.
He pointed to several meetings the campaign had with prison managers and politicians, including federal ministers.
"This was a fully democratic process," Skoropada said.
Masse said he would make his ruling March 5.
Also charged are Jesse Archibald, Gerry Capelle, James Masse, Thorsen Hansgen, Lindsey Pilon and Patrick Thompson.