Defense attorneys representing the 15-year-old boy accused of killing five family members last month in Fall City are arguing their client’s version of events are “forensically viable,” according to court documents.

The 15-year-old was charged Oct. 24 with five counts of first degree murder and one count of first-degree attempted murder after a mass shooting at his family’s Fall City home Oct. 21. He is accused of killing his parents, Mark and Sarah Humiston, as well as his siblings, Katheryn Humiston, 7, Joshua Humiston, 9, and Benjamin Humiston, 13.

In a court document filed Oct. 28, public defense attorney Amy Parker said there are two versions of what happened: her client’s and that of the sole living victim, the suspect’s 11-year-old sister.

The charging documents state that the 15-year-old suspect had called 911 at 4:55 a.m. Oct. 21, claiming his 13-year-old brother killed the family before killing himself. At 5:02 a.m., the police received a second call from the Humiston family’s neighbor. The 11-year-old had run to the neighbor’s house for help after finding her family members shot and allegedly getting shot at by the suspect.

The charging documents also state that, based on the evidence found at the scene and during the autopsies, and given the 11-year-old’s police statement, it appears the suspect staged the scene before first responders arrived.

Parker wrote in an Oct. 28 document that after reviewing the crime scene in person, she doesn’t believe anyone involved in the shooting could have left the scene without blood on them, and there is so far no evidence that indicates the suspect did have blood on him.

“It is corroborated he called 911, it doesn’t appear [he] had any forensics on his body and there does not appear to be any motive outlined,” Parker wrote.

The children’s maternal grandmother, who is now the 11-year-old’s guardian, is the trustee of the Humiston Fall City home. She scheduled hazmat cleaning of the residence for Oct. 26, but it was canceled after the defense team asked for an emergency preservation order and requested to investigate the scene further.

“It is my experience that law enforcement can and does engage in bias investigations when they think they have the ‘right’ suspect,” Parker wrote in the Oct. 28 document. She added that she would like the defense to have an opportunity to investigate the crime scene “free from this bias.”

The court allowed the defense to enter the home for 10 hours on Oct. 29. The team was allowed access to items in plain view, but was not allowed to search things like cabinets, containers, drawers or digital devices. The defense also brought its own forensic expert to take a digital 3D scan of the premises.

The suspect appeared in court for the first time Oct. 25, where King County prosecutors requested a discretionary decline hearing, in which the judge decides if the case should be tried in juvenile court or transfer to adult court. The decline hearing is set for June, with a status conference scheduled for January.

Court documents filed Nov. 1 state that Parker and the suspect’s other public defense attorneys withdrew because the suspect “retained other counsel.” There are no additional details.