The Karen Read trial begins its seventh week Monday, and the jury has yet to hear from the lead investigator on the case, Trooper Michael Proctor.

Defense Attorney Peter Elikann said it’s highly unusual for a lead investigator not to testify — or even to hold off testimony for so long. But, he said, there’s a reason for that.

Video Video, updates: New evidence shown as detective’s testimony continues in Karen Read trial

“He’s viewed as not being particularly impartial, that he probably should have taken himself out of the investigation at the beginning,” Elikann said. “When he personally knew and was so connected to so many people inside that house.”

‘That house’ would be 34 Fairview Avenue in Canton, formerly owned by now-retired Boston police officer Brian Albert. The prosecution alleges Karen Read committed second-degree murder when she backed into her boyfriend, Boston police officer John O’Keefe, after dropping him off at that house on the night of January 29, 2022. Prosecutors say Read let O’Keefe die in the snow — after the two had an argument.

The defense aims to prove that O’Keefe was actually murdered by someone inside 34 Fairview Avenue — then tossed into the snow.

Elikann said that the defense has done a good job, thus far, at raising reasonable doubt as to Read’s guilt. That was on display last week when Proctor’s supervisor, State Police Sergeant Yuri Bukhenick testified for two days. (He may also continue testimony Monday.

“He was a rather good, articulate spokesperson,” Elikann said. “At the same time, every one of these people that testifies there’s two sides to it. There’s sort of a pro-prosecution, pro-defense side to it.