A Norwell woman is accused of interfering with a State Police murder investigation and taping related grand jury testimony, authorities said.

Brianne St. Peter McMahon, 36, was indicted Wednesday by a Plymouth County Grand Jury on charges including wiretapping and misleading a police investigation, according to the office of Plymouth District Attorney Timothy J. Cruz.

In October 2015, McMahon allegedly slipped her cellphone into the pocket of a witness, who was set to appear before a grand jury at Brockton Superior Court, to record the proceedings and interviews related to the murder of 45-year-old Robert McKennacq, according to Cruz’s office.


Later that afternoon, State Police seized the phone from the witness, a friend of McMahon’s who was unaware the device had been placed in her pocket, according to the indictment.

When McMahon came to the Brockton district attorney’s office to retrieve her lost phone, she was interviewed by State Police and arrested, Cruz’s office said.

McMahon is charged with three counts of wiretapping, one count of misleading a police investigation, and one count of distribution of transcript or distribution of grand jury testimony with intent to interfere with criminal proceedings, according to the indictment.

McKenna was discovered dead at his home on Damons Point Road in Marshfield in September. Four people face charges in connection with his murder, according to Cruz’s office.

Rachel Riley can be reached at rachel.riley@globe.com. Follor her on Twitter @rachel_m_riley.