The parents of Idaho student murder suspect Bryan Kohberger have been subpoenaed to testify before an investigative grand jury in the family’s home state of Pennsylvania, says a report. Mr Kohberger’s father is expected to testify before the grand jury in a sealed proceeding in Monroe County on Thursday, a source told CNN. His mother has already given evidence to the grand jury, the source told the news outlet and added that their testimony, which will be given under oath, may be shared with Idaho prosecutors. Pennsylvania judges are permitted to share transcripts of grand jury witness testimony with other law enforcement agencies. A lawyer for Mr Kohberger’s parents, Michael and Maryann Kohberger, tried unsuccessfully to have the subpoenas cancelled, the source told CNN. Mr Kohberger is accused of brutally killing Kaylee Goncalves, 21, Madison Mogen, 21, Xana Kernodle, 20, and Ethan Chapin, 20, on 13 November in a horror attack that rocked the college town of Moscow and sent shockwaves across America. Mr Kohberger appeared in court for his arraignment in Latah County Court in Moscow, Idaho, on Monday. During the arraignment, he refused to enter a plea on four counts of first-degree murder and burglary with his attorney Anne Taylor saying that he was “standing silent” on the charges. The judge entered not guilty pleas on his behalf. Mr Kohberger’s sister feared that her brother was involved in the stabbings of four University of Idaho students before police swooped on their parents’ home in December and arrested him for murder, according to a new report. Sources told NBC’s Dateline that one of the accused killer’s older siblings grew increasingly suspicious of her brother and his behaviour when the family gathered to spend the holidays together. Her suspicions were so great that – at one point – several family members searched Mr Kohberger’s white Hyundai Elantra for possible evidence of the crime, they said. Read More Families of slain University of Idaho students prepare to sue college over murders Idaho murders – update: Bryan Kohberger’s alleged victims’ families prepare to sue Moscow Four students stabbed to death, a weeks-long manhunt and still no motive: What we know about the Idaho murders Bryan Kohberger ‘stands silent’ and refuses to enter plea in murders of four Idaho college students Bryan Kohberger’s sister searched his car for evidence before police swooped in