The juror had said it would be difficult to convict the ex-player without a murder weapon and discussed inadmissible evidence, Garsh noted.
The judge dismissed the juror after ordering the public out of the Massachusetts courtroom for a hearing that included defense lawyers, prosecutors, witnesses and the juror.
The closed-door session was "no broader than necessary to protect Hernandez's right to a fair trial," Garsh said.
After the hearing, Garsh also said there was "credible evidence" that the dismissed juror had expressed interest in being part of the Hernandez jury and had attended more Patriots games than the juror admitted on a questionnaire.
"The juror's recollection of conversations is not supported by the credible evidence," the judge said.
The juror's presence on the jury "posed a substantial risk" to the fairness of the trial, she added, and the dismissal was necessary in "the best interest of justice."
Hernandez, 25, pleaded not guilty
in the 2013 killing of former semipro football player Odin Lloyd, 27, who dated the sister of Hernandez's fiancee.
Two alleged accomplices, Ernest Wallace and Carlos Ortiz, have pleaded not guilty and will be tried separately.
Witness returns to the stand
The trial resumed Tuesday afternoon, with Shaneah Jenkins, 23, who was dating Lloyd at the time of his death, returning to the witness stand.
Her sister, Shayanna, is Hernandez's fiancee and mother of his child.
On Tuesday, Shaneah Jenkins broke into tears when she recalled a call from a state trooper with word that "Odin was dead."
Shaneah Jenkins testified that she later visited her sister and saw Hernandez, who placed his hand on her shoulder to console her.
Hernandez told her "he's been through this death thing before and it would all get better with time," she testified.
After Hernandez left the home, Shaneah Jenkins testified, her sister Shayanna kept receiving cell phone calls and text messages. Shaneah Jenkins said her sister seemed "secretive," her responses "very short."
Shayanna Jenkins would go to the basement to continue the conversations, her sister testified.
One time, Shaneah Jenkins told the jury, her sister went down to the basement with what appeared to be a new garbage bag folded in her hand.
Shayanna later left the house, returned and asked to borrow her sister's car, Shaneah Jenkins testified.
The sister, who had never borrowed Shaneah Jenkins' car before, said she was going to the bank to get money for the housekeepers, according to Shaneah Jenkins.
Last week, Shaneah Jenkins testified that she introduced Lloyd to Hernandez on her birthday in August 2012.
Jenkins told the jury that Lloyd and Hernandez were in the "beginning stages of a friendship."
She said the two men and others would gather in Hernandez's basement "man cave" -- with fitness and theater rooms, a bar and pool table emblazoned with the Patriots' logo -- to smoke marijuana.
But Jenkins said she was not aware of her boyfriend and Hernandez ever getting together outside of the home except for the day Lloyd was killed.
In opening statements Thursday, defense lawyer Michael Fee said the two men were close friends and that Hernandez had no reason to kill Lloyd.
Fee described the victim as one of his client's "partying pals" who was known as the "blunt master'' for the marijuana cigars he often procured for Hernandez. The two men could have been brothers-in-law, he said.
"Aaron Hernandez is not the murderer of his friend," Fee said. "In June 2013, Aaron Hernandez was planning his future, not a murder."
The case has divided the Jenkins sisters, who sit on opposite sides of the courtroom -- Shaneah with Lloyd's mother and Shayanna with Hernandez's family.
Prosecutor Patrick Bomberg has told the jury that Hernandez not only orchestrated the killing, but also participated in it and covered it up.
Bomberg summed up the prosecution's largely circumstantial case, telling the jury that Hernandez and his associates killed Lloyd and then "took evidence with them and tried to and, in some cases, were successful in destroying evidence."
The three picked up Lloyd and drove to a secluded area where he was shot and killed, Bomberg said.
A marijuana blunt found near Lloyd's body had traces of both his DNA and that of Hernandez, Bomberg said. Hernandez's DNA also was found on a .45-caliber shell casing found in a car he had rented.
A footprint at the industrial park where Lloyd's body was found matched sneakers worn by Hernandez, the prosecutor said.
Lloyd, who was shot six times, was shown in photos on his back in the industrial park where his body was found.
Defense: Targeted for celebrity status
The defense said the one-time NFL star worth $40 million was targeted by police and prosecutors in the death of the semipro football player because of celebrity status.
Hernandez "never had a chance" as authorities zeroed in, Fee told the jury.
"As soon as they found out Aaron Hernandez -- a celebrity football player for the New England Patriots -- was a friend of Odin Lloyd's, it was over," he said.
On June 16, 2013, Lloyd was riding with friends
in a black Chevrolet Suburban, which police later learned was rented by Hernandez.
Close friend Daryl Hodge was with Lloyd when he said Lloyd got a text from Hernandez, asking to hang out later that night.
As they parted ways, Lloyd told Hodge he'd see him later.
Lloyd's body was found the next day.
The judge has blocked any mention that Hernandez was indicted in two other killings in Boston. Hernandez pleaded not guilty in the shooting deaths of Ernesto Abreu and Safiro Furtado outside a bar in Boston in 2012. A trial date hasn't been set.