PORTLAND, Ore. -- A grand jury this is expected to consider murder charges against a 16-year-old accused of killing his 14-year-old girlfriend.

Law enforcement sources tell KGW that friends of both Yashanee Vaughn, the victim, and Parrish Bennette, the accused killer, will be asked to testify about their relationship.

The grand jurors will also hear about evidence seized when police executed search warrants at Bennette's home, where they believe Vaughn was attacked, and another location. They are also expected to hear from forensic experts at the Oregon State Police Crime Lab who analyzed the evidence.

Meanwhile, on Sunday, searchers wrapped up a third day at Rocky Butte State Park where they had hoped to find Vaughn's body.

More: Search for Vaughn's body

Bennette was arrested Thursday after lab results linking him to her death came back. He was charged with manslaughter Friday.

A juvenile court judge reduced the charges against Bennette, who had been charged with murder.

Investigators believe Vaughn was killed by Bennette onMarch 19th in his home.

Bennette pleaded not guilty in juvenile court Friday afternoon and the charge was lowered to manslaughter. His appearance drew a standing room only crowd to the court. Bennette was expected to be tried as an adult. His bail was set at$500,000.

Vaughn was reported missing by her mother Shaquita Louis on March 21. She was last seen March 18waiting for a bus near a TacoBell on NE82nd Avenue.

Family and friends became concerned after there had been no contact from her by phone, or updates on her Facebook page.

Two search warrants were served Monday at Bennette's home. Blood found in the home matched the DNA of Vaughn, law enforcement sources said. He was on juvenile probation at the time of the death.

Photos: Vaughn murder investigation

There could also be more arrests to come, investigators said.

This is a terrible tragedy and I wish our officers and detectives had more time to interdict this terrible incident, but that wasn t the case, Chief Michael Reese said.

Police timeline of Vaughn case

The victim's family and friends gather outside her home Thursday afternoon

More: Family disputes how police initially handled case

(KGW Reporters Anne Yeager, Mike Benner and Assignment Editor Colin Miner contributed to this report.)

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