Lead investigator in wrong-apartment killing says he doesn't believe Amber Guyger committed a crime Botham Jean, 26, was shot to death in his own apartment in Dallas.

The lead investigator in the wrong-apartment killing of an innocent man by a former Dallas police officer on trial for murder claimed on Wednesday that the officer did not commit a crime based on the totality of the evidence.

The stunning pronouncement by Texas Ranger David Armstrong, the lead homicide investigator on the high-profile case, came while he was under cross-examination by an attorney for fired police officer Amber Guyger but not while the jury was present in the courtroom.

"After finishing your investigation and looking at the totality of the circumstances, and considering everything, do you believe today that you have probable cause to believe that Amber Guyger committed a crime?" defense attorney Robert Rogers asked Armstrong, who replied, "Based on the totality of the circumstances, based on the complete investigation, no sir."

Guyger, 31, is charged with murder stemming from the Sept. 6, 2018, fatal shooting of 26-year-old Botham "Bo" Jean at the South Side Flats apartment complex in Dallas.

Guyger, who was fired from the Dallas police department 18 days after Jean was killed in his own apartment, claimed she mistook the victim's apartment for her own, which was one floor below and had an identical layout.

Not only did she mistakenly park on the wrong floor of the complex, she walked down a long hallway, passing 16 different apartments but failed to realize she was not headed to her front door, a prosecutor said during his opening argument on Monday.

Prosecutors said Guyger, who had just gotten off duty after working more than 13 hours, acted recklessly on the night of the shooting and was distracted, suggesting from her text messages that she was planning to have a rendezvous with her police partner and lover. Prosecutors said she failed to recognize numerous hints that she was headed to the wrong apartment, including failing to realize she was standing on a red mat before entering Jean's apartment door, which she found unlocked and ajar.

Armstrong said the evidence did not support the prosecution's claims that Guyger was reckless.

When asked to express his opinions on the evidence collected, prosecutors raised an objection and Dallas County District Court Judge Tammy Kemp sent the jury out of the courtroom.

Without the jury in the courtroom, Kemp allowed Rogers to proffer Armstrong's opinions on the investigation but refused to allow him to state those opinions in front of the jury, at least for the time being.

Rogers reserved the right to recall Armstrong as an expert witness for the defense, which would set up the awkward situation of the prosecution trying to discredit the testimony of the lead investigator in their case.

Armstrong testified that in his opinion, Guyger believed that she had encountered a burglar in what she wrongly thought was her own apartment.

"Do you have an opinion as to whether it was reasonable, based on the facts and circumstances, for an ordinary and prudent person in Amber Guyger's position, for her to perceive Botham Jean was a deadly threat?" Rogers asked Armstrong.

He responded, "I believe that she did perceive him as a deadly threat."

Continuing his cross-examination, Rogers asked, "And today you're telling us that based on everything and based on your training and experience, you don't believe there's even probable cause that Amber Guyger committed any crime, correct?"

Armstrong replied, "That's correct."

Rogers continued, "And do you have an opinion as to whether Amber Guyger was reckless or criminally negligent when she parked on the fourth floor, when she walked to apartment 1478, when she entered apartment 1478 and when she encountered (Jean), perceived him as a deadly threat and shot him?"

Armstrong replied, "No, I don't believe that it was reckless or criminally negligent based on the totality of the investigation and the circumstances and facts."

Armstrong was also asked what goes through an officer's mind when confronted by someone they believe to be a potentially deadly suspect.

"Based on my training and my experience, physically your heart rate goes very very high," Armstrong said. "Your vision becomes narrowed, which is commonly referred to as tunnel vision. You begin to think very very quickly and because your vision is narrowing you begin to concentrate on what you believe your threat is. You narrowly concentrate on that threat and that's due to blood rushing to the major organs of the body because your body is saying, 'I need to do this right now, which is either fight or flight."

Dallas County Assistant District Attorney Jason Hermus objected to allowing the jury to hear Armstrong's opinions on the evidence or attempt to describe what was going through Guyger's mind at the time of the shooting.

"First and foremost, I think it's inappropriate even for a qualified expert to be testifying as to what they believe the state of mind of the defendant was at the time of the commission of the offense. Even a qualified expert is not allowed to do that in the state of Texas," Hermus told Judge Kemp.

"Secondarily, what Ranger Armstrong believes is Ranger Armstrong's opinion," Hermus told Kemp. "The fact that he believes something based on evidence, doesn't mean that the jury is going to believe the same thing. All it would do is serve to confuse them and possibly even override their individual assessment as the exclusive judges of the facts and the evidence because of his station as a Texas Ranger."