Friends and former co-workers were among the eight witnesses called to testify about the growing, storage and sales of marijuana for the three G3 locations.
Afterward, Assistant U.S. Attorney Jay Robinson rested his case.
Sandusky, who also had a warehouse in Ontario, is facing six counts of drug trafficking, which can carry a sentence of 10 years to life in prison.
In addition to G3 co-founder John Leslie Nuckolls II and warehouse worker Richard Irwin Kirchnavy, DEA special agents and sheriff's deputies testified for the government.
"One warehouse, three retail stores and over 1,000 marijuana plants - evidence for a reason why the defendant is guilty as charged," said Robinson, during opening statements Tuesday, which outlined an alleged conspiracy among Sandusky and other defendants to cultivate and sell marijuana through the cooperatives.
Sandusky and five others affiliated with G3 were arrested and indicted in June on federal drug-trafficking charges as well as conspiracy to manufacture and possess with intent to distribute marijuana.
The defendants, including Sandusky's brother Keith, were also charged with possession with intent to distribute marijuana.
Nuckolls, 31, of Rialto and Kirchnavy, 45 of Rancho Cucamonga has earlier pleaded guilty and accepted a plea bargain, which included testifying during the trial.
Nuckolls testified he had been friends with Sandusky for about 11 years. In 2009 he approached Sandusky, who had real estate and broker experience, about opening a medical marijuana dispensary.
"We both had medical issues. We were both going to places to get medication," Nuckolls said. "We figured we could provide better service for our patients."
They opened their first location, a 2,000-square-foot store, that year in Upland. Nuckolls was the chief financial officer, Sandusky was chief executive officer.
Later they rented a 2,000 square-foot warehouse just one street away where they grew a little more than 100 plants to stock the store, Nuckolls said.
About a year later, they opened a 1,500-square-foot dispensary in Moreno Valley and not long after that a similar-sized location in Colton.
"From 2009 into 2010, the Upland store serviced about 500 people," Nuckolls testified, adding that the Moreno Valley store had double that number of patients.
With the growth of business, G3 rented a 40,000-square-foot warehouse in south Ontario in 2011, which was used to grow marijuana and stock the stores, he testified.
"We wanted to make sure we were able to produce enough medication for all three stores," Nuckolls said. "We wanted a quality product, and we wanted to control it ourselves."
On Nov. 1, 2011, the warehouse was raided, and officials discovered about 1,200 marijuana plants.
Officials on the stand called the large indoor grow a sophisticated operation.
Nuckolls testified that he resigned from the business on Nov. 18, 2011, leaving Sandusky in charge.
Robinson asked Nuckolls if, in June 2009, he was working as a confidential informant for the San Bernardino County Sheriff's Department.
"I was not," Nuckolls, who added that he talked with the agency, along with San Bernardino County District Attorney's Office and the DEA, and worked with them, but never worked as an informant.
Robinson then pointed out that Nuckolls had an agreement with the DA's Office at that time and after helping them with cases had a felony charge dismissed.
Kirchnavy, who also took the stand on Wednesday, said he started growing marijuana for Sandusky in 2009 at the defendant's house.
"In the beginning, the marijuana grown in the closet was for personal use, but once Upland G3 opened, the plants went to the store," he testified.
Sandusky hired him to grow the plants for $800 a week. Between June 2010 and November 2011, Kirchnavy testified that his salary grew to $2,000 per week.
Roger Jon Diamond, Sandusky's lawyer, asked Kirchnavy to describe his decision to grow marijuana for money.
"Very poor," said Kirchnavy, who later pleaded guilty to cultivating, manufacturing and distributing marijuana plants.
Kirchnavy testified that after the Ontario warehouse was raided, Sandusky talked to him about opening a new warehouse to once again grow marijuana and asked if he would cultivate.
Kirchnavy's response? "You're crazy."
During the trial, Diamond spent a considerable amount of time doubting the policy of regulations of the officials who raided the Ontario warehouse and questioned the amount of vegetation found and whether they were viable marijuana plants.
Sandusky took the stand for about five minutes Wednesday and will continue his testimony today.