TULSA, Okla. (AP) — A judge declined to replace the prosecutor overseeing the case against one of two Oklahoma brothers accused of killing their parents and three siblings.

District Judge Sharon Holmes ruled Tuesday that there isn't evidence of improper behavior by Tulsa County Assistant District Attorney Sarah McAmis and that she can remain on the case against Michael Bever.

An internal investigation determined last month that former Broken Arrow Police Detective Gayla Adcock had "grossly mishandled" evidence in the case and Bever's lawyer, Corbin Brewster, accused McAmis of involvement in the evidence mishandling.

Brewster said he's hoping for a fair trial for Bever, 19, who faces murder charges in the 2015 stabbing deaths of his parents and three of his siblings and an assault charge in the stabbing of a sibling who survived the attack. Bever's older brother, Robert Bever, pleaded guilty in 2016 and was sentenced to life in prison.

"We're going to give it our best shot and we're going to keep fighting for Michael," Brewster said.

Adcock resigned this year during an investigation into her actions when a hard drive with potentially significant evidence was lost on her watch. In her testimony, she said she's baffled and has been trying to figure out what happened to that evidence.

Holmes ruled that there was no correlation between McAmis' actions and those of Adcock.

Michael Bever's trial is scheduled to begin Monday.