They found Bever guilty of five charges of first-degree murder and a count of assault and battery with intent to kill after more than five hours of deliberation.
Bever is accused of helping his brother, Robert Bever, kill their parents and three of their siblings in their Broken Arrow home in 2015, when he was 16. Robert Bever later pleaded guilty and received a life sentence without the possibility of parole.
The prosecution's closing arguments included the presentation of a jailhouse journal entry that said, "Once upon a time there were brothers named Robert and Michael. They hated their family and they killed them. The End."
Prosecutors asked jury members not to let sympathy concerning Michael Bever's home life impact their deliberations. They said that even if jurors didn't believe that Michael had actually stabbed anyone, they believe jurors will find that he had helped his brother plan and carry out the killings.
According to prosecutors, no evidence showed that Michael Bever tried to stop the slayings.
They said Robert's testimony consisted of lies and that Michael had acted like a guilty person, never running or trying to call for help and even hanging up on a 911 call.
The defense agreed that the situation is overwhelming, but claimed there was not a lot of blood on Michael and said the murders were the result of his brother's descent into mental illness.
They said Michael was abused and showed that he was shocked when his brother carried out the slayings. They pointed out he was not wearing body armor like his brother was after the incident and claimed that the forensic evidence did not match the state's claims.
Defense attorneys said that the only thing that would have been different if Michael Bever had tried to stop his brother was that he also would have been killed.
Jury deliberation began around 5 p.m. Wednesday afternoon.
Around 10 p.m., jurors reportedly asked the judge a question. The judge told them that they were to consider all six charges as acts committed "in concert with each other in principal to the crime."
They reached a verdict before 11 p.m. and found Michael Bever guilty of all six charges.
The jury will discuss sentencing Thursday.
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