Superior Court Judge Susan Garsh cut off testimony at about noon ET after a court officer alerted her to the threat. She told jurors there would be a brief delay and they were led from the courtroom. Then she announced that the building was being evacuated.
The Fall River Justice Center was swept by Massachusetts State Police. No explosives were found, and employees were let back in about an hour later. Court resumed at 2 p.m., with Garsh telling jurors that there was no reason to believe the interruption was related to the Hernandez case.
Jurors were held in a building across the street during the closure. Security officers said Hernandez was taken out of the building but did not say where he was held.
Meanwhile, two people with knowledge of the matter told The Associated Press that Shayanna Jenkins, Hernandez's fiance, will be called to testify Friday.
Jenkins was granted immunity by the court in February, which means she can be compelled to testify or else face time behind bars. There had been a question over whether prosecutors would call Jenkins, who has been in a relationship with Hernandez since high school and is the mother of his 2-year-old daughter.
Jenkins has pleaded not guilty to perjury. Prosecutors say she lied to a grand jury investigating the June 17, 2013, killing of Odin Lloyd, who was dating her sister. Lloyd was found shot to death at an industrial park less than a mile from the home that Jenkins and Hernandez share.
Video surveillance viewed by jurors showed Jenkins removing what appeared to be a box from the family's basement the day after the killing. Prosecutors said before the trial they believe the box contained the gun Hernandez used to kill Lloyd, which has never been found.
Jenkins has been coming to court sporadically and sitting behind Hernandez, whispering "I love you," to him at breaks and occasionally joking with him. At times, she has chatted with his lawyers and occasionally passed them notes. She has not appeared in court since March 6. That day, she was not wearing a large diamond engagement ring that was usually seen on her ring finger.
Also Thursday, the court released Garsh's decision that prosecutors may introduce into the trial jailhouse calls Hernandez made in which he discusses giving money to a cousin. Prosecutors say the promises of money were used to buy her silence after the killing.
Garsh said she would also allow a July 12, 2013, call in which Hernandez, speaking from jail, tells his cousin Tanya Singleton: "Obviously don't say nothing."
"I'm not saying nothing," she replies.
Singleton, who has terminal cancer, spent seven months in jail for refusing to testify before the grand jury investigating Lloyd's killing. She has also pleaded not guilty to helping Hernandez co-defendant Ernest Wallace flee to Georgia.
In a July 23, 2013, conversation from behind bars, Hernandez is recorded saying he set up trust funds of $75,000 or $100,000 for Singleton's two sons, which he says would double every seven years.
But in actuality, he never set up the trust funds.
Singleton's sister, Jennifer Mercado, completed her testimony in the case Thursday. Mercado, who was granted immunity and ordered by the court to testify, said on the stand this week that Wallace and Hernandez's other co-defendant, Carlos Ortiz, sometimes smoked PCP and that Wallace would act crazy, jittery and erratic.
She said surveillance video taken at Hernandez's home in the early morning hours before the killing showed the two men acting jittery. But upon seeing more video Thursday from that morning and later that day, Mercado said it did not appear that Wallace and Ortiz were acting erratic or crazy.
Wallace and Ortiz have pleaded not guilty and are being tried separately.
The Associated Press contributed to this report.
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